International Workshop on Future Linear Colliders, LCWS2024

8 Jul 2024, 08:00 → 11 Jul 2024, 20:00 Asia/Tokyo

The University of Tokyo, Japan

The 2024 International Workshop on Future Linear Colliders (LCWS2024) continues the series devoted to the study of the physics, detectors, and accelerator issues relating to high-energy linear electron-positron colliders. A linear collider will initially operate as a Higgs factory, and provides a clear path for upgrades in energy and luminosity. Since the last workshop (LCWS2023), many significant steps have been made. With a wide program of plenary and parallel sessions, this workshop will provide an opportunity to present ongoing work and to get informed and involved.

The workshop is scheduled from the morning of 8th of July to the late afternoon of 11th of July, at the University of Tokyo (Hongo campus) located in the heart of Tokyo. The day after the main workshop, Friday 12th July, is available for satellite meetings related to the workshop.

In-person attendance at the workshop is strongly encouraged, however remote participation will be possible, with a reduced registation fee.

Key dates

• Early February 2024: Registration and abstract submission opens
• April 26th: Abstract submission deadline
  (Further submissions may be considered depending on conveners)
• April 29th: Student support (waived registration) application (2nd) deadline
  (Further applications can be considered until filled)
• May 31st: Early registration deadline (extended)
• June 30th: Final registration deadline
• July 8th: Workshop begins 

 

The workshop is co-hosted by ICEPP (U. Tokyo) and KEK.

 

Sponsors

 

LCWS2024_poster.pdf

Monday, 8 July

08:30 → 09:00 Registration

09:00 → 10:30 Plenary: Opening 1

Convener: Jim Brau (University of Oregon (US))

09:00 Opening remarks

Speaker: Shoji Asai (University of Tokyo (JP))

09:10 Physics case for Higgs and Electroweak precision

Speaker: Jorge De Blas Mateo (Universidad de Granada (ES))

09:30 ILC status

Speaker: Tatsuya Nakada (EPFL - Ecole Polytechnique Federale Lausanne (CH))

09:42 CLIC status

Speaker: Steinar Stapnes (CERN)

09:54 Status of the C3 R&D

Speaker: Caterina Vernieri (SLAC National Accelerator Laboratory (US))

10:06 Physics case for e+e- at 500 GeV and above

Speaker: Georg Ralf Weiglein (Deutsches Elektronen-Synchrotron (DE))

10:30 → 11:00 coffee

11:00 → 12:40 Plenary: Opening 2

11:00 HALHF status

Speaker: Brian Foster (University of Oxford (GB))

11:12 XCC status

Speaker: Tim Barklow (SLAC National Accelerator Laboratory (US))

11:24 Energy recovery at a Linear Collider

Speaker: Vladimir Litvinenko

11:36 CEPC status

Speaker: Jie Gao (IHEP)

11:48 FCCee status

Speaker: Frank Zimmermann (CERN)

12:00 Muon collider status

Speaker: Daniel Schulte (CERN)

12:12 Higgs Factory detector R&D

Speaker: Srini Rajagopalan (Brookhaven National Laboratory (US))

12:40 → 12:50 Workshop photo

12:50 → 14:00 ATF EB meeting

Speaker: Dr Nobuhiro Terunuma (KEK)

12:50 → 14:00 Lunch

14:00 → 15:30 Accelerator Plenary

Convener: Hiroshi Sakai (KEK)

14:00 ITN: accelerator developments

Speaker: Shinichiro Michizono (KEK)

14:15 CLIC: accelerator developments

Speaker: Philip Burrows

14:30 C3: accelerator developments

Speaker: Ankur Dhar (SLAC National Accelerator Lab)

14:45 CEPC: accelerator developments

Speaker: yuhui li

15:00 FCCee: accelerator developments

Speaker: Frank Zimmermann (CERN)

15:15 Energy Upgrades of a linear Higgs factory

Speaker: Emilio Nanni (SLAC National Accelerator Laboratory)

14:00 → 15:30 Physics & Detector plenary

Convener: Ritchie Patterson (Cornell University (US))

14:00 ECFA Higgs-EW-top factory study

Speaker: Aidan Robson (University of Glasgow (GB))

14:15 Beyond collider experiments at a Linear Collider

Speaker: Yasuhito Sakaki (KEK)

14:30 Challenges for MC generators

Speaker: Jürgen Reuter (DESY Hamburg, Germany)

14:45 Opportunities and Experimental Challenges at the Higgs-Top interface

Speaker: Junping Tian (University of Tokyo)

15:00 Highlights from LHC detector upgrades

Speaker: Gustaaf Brooijmans (Columbia University)

15:15 Highlights from detectors for EIC

Speaker: Taku Gunji (University of Tokyo (JP))

15:30 → 16:00 coffee

16:00 → 17:30 Plenary: Open discussion sesson - Global Vision for a Linear Collider facility

Conveners: Jenny List (Deutsches Elektronen-Synchrotron (DE)), Steinar Stapnes (CERN)

17:30 → 19:30 Posters: Posters and Reception

17:30 Exploring the Electromagnetically Interacting Dark Matter at the International Linear Collider

Dark Matter being electrically neutral does not participate in electromagnetic interactions at leading order. However, we discuss here fermionic dark matter (DM) with permanent magnetic and electric dipole moment that interacts electromagnetically with photons at loop-level through a dimension-5 operator. We discuss the search prospect of the dark matter at the proposed International Linear Collider (ILC) and constrain the parameter space in the plane of the DM mass and the cutoff scale $\Lambda$. At the 500 GeV ILC with $4$ ab$^{-1}$ of integrated luminosity we probed the mono-photon channel and utilizing the advantages of beam polarization we obtained an upper bound on the cutoff scale that reaches up to $\Lambda = 3.72$ TeV.

Speaker: MANISH KUMAR SHARMA (Birla Institute of Technology and Science pilani, Goa Campus)

17:40 A CP violating top-Higgs coupling with SMEFT in the Feynman-Diagram gauge

We calculate the cross section for the process $\mu^-\mu^+\to \nu_\mu\bar{\nu}_\mu t\bar{t}H$ with complex top Yukawa coupling, which can be obtained by adding a gauge invariant dimension-6 operator to the Standard Model (SM) Lagrangian. The Feynman-Diagram (FD) gauge and the unitary (U) gauge amplitudes give exactly the same cross section, and subtle gauge theory cancellation among diagrams in the U gauge at high energies is absent in the FD gauge, as has been observed for various SM processes. In addition, we find that the total cross sections at high energies are dominated by a single, or a set of non-vanishing Feynman amplitudes with the higher dimensional vertices in the FD gauge.

Speaker: Ya-Juan Zheng

17:40 A New Method for Measuring the Higgs Mass at ILC

The Higgs mass as one of the fundamental parameters in the Standard Model has been already measured pretty well by the data collected so far at the LHC. However in some cases of looking for small deviations from the SM, current precision or projection of the Higgs mass measurement at the LHC or HL-LHC may not be good enough. One prominent example is for the SM prediction of the Higgs partial decay width to WW or ZZ, in which the Higgs mass uncertainty becomes one of the leading sources of parametric theory error. It is expected that at future e+e- colliders we can improve the Higgs mass precision significantly by the well-known “recoil mass method”, at least statistically. This research proposes a new method which may complement to the recoil mass method in terms of systematic errors. The new method employs the signal channel of Higgs decaying to a pair of fermions, in particular tau leptons, and makes use of transverse momentum conservations alone instead of the 4-momentum conservation in the recoil mass method. The key experimental observables will be just the momentum directions of tau leptons without any input from energy measurement, and the momentum directions can possibly be measured by reconstructing the decaying vertex of the tau leptons. This new method can in principle be applied at the LHC as well. We will explore this method by performing realistic detector simulation and physics analysis at the ILC.

Speaker: Thomas Berger

17:40 Advancing Timing Resolution of Strip Scintillators for Electromagnetic Calorimeters

In the upcoming generation of collider experiments, such as the proposed Linear Collider Higgs Factory, precise measurement of particle flow (PF) is pivotal for enhancing the energy resolution of jets, which consist of numerous hadrons observed in the final state. To achieve this, we focus on equipping fine-segmented electromagnetic calorimeters with high-precision time measurement capabilities, thereby facilitating improved discrimination of particles within jets and aiding in cluster reconstruction within the jet calorimeter.
In our research, we emphasize the essential role of electromagnetic calorimeters with highly-segmentation, necessitating a cell size of 5 mm x 5 mm. By enhancing each cell with high-precision time measurement, we aim to advance the accuracy of energy measurements and improve the identification of parent particles within jets. Furthermore, our approach holds promise for exploring Beyond the Standard Model (BSM) physics, particularly in the detection of long-lived particles.
To achieve these objectives, we have developed a novel configuration for the electromagnetic calorimeter, employing scintillator strips arranged orthogonally to ensure both positional resolution and a reduced number of readout channels. The scintillator strips have been read out the scintillation light at the both end edges by serially connected silicon photo-sensors. This configuration increase the photons and improve the time resolution. Various configurations are tested at the beam test at KEK. Moreover, our measurements are anticipated to refine the accuracy of time measurements within electromagnetic showers. Through electron beam tests, we have demonstrated significant improvements in time resolution performance. In this presentation, we will showcase the results of our efforts to enhance the optical readout method of the current strip scintillator for electromagnetic showers, thereby advancing the capabilities of linear collider Higgs Factory collider experiments.

Speakers: Mr Masamune Ishitani (Shinshu University), Tohru Takeshita (Shinshu University (JP))

17:40 Laser and plasma accelerator research for high energy physics at the BELLA Center

The BELLA Center has been pursuing laser and laser-plasma accelerator (LPA) research for high energy physics. One of the ultimate goals is to provide a building block for future linear colliders. At the flagship 1-Hz 1-PW laser facility, the development of a 10-GeV class LPA module is ongoing, and such modules in series are envisioned as the path to a high energy collider at TeV energies and beyond. To achieve the desired luminosities required for such a collider, high repetition-rate (tens of kHz) laser sources are needed. To meet these requirements, the BELLA Center is pursuing a promising technology based on the coherent combining of fiber lasers. In this presentation, the current status of those researches are discussed.

Speaker: Kei Nakamura (Lawrence Berkeley National Laboratory)

17:40 Optimal Collision Energy for Higgs Precision Measurements at the ILC250

The ILC is currently proposed to be running at 250 GeV at the initial stage, based on the fact that the cross section of the leading Higgs production channel (ZH) peaks at more or less 250 GeV. Due to the effects of beamstraglung and initial state radiation which shift the effective center of mass energies, the more optimal collision energy has not been known yet. First, we will carry out analyses of the ZH cross section measurement and evaluate the impact of the collision energy by a scan between 240 to 260 GeV. Second, the effects of anomalous Higgs couplings between Higgs and ZZ are momentum-dependent, thus very much sensitive to the collision energies. More over, having the anomalous HZZ couplings measured at a couple of energy points may provide significant improvement due to the large correlation between anomalous and SM-like HZZ couplings. We will carry out such studies and propose a new scenario of collision energy for the ILC250.

Speaker: Andrea Siddharta Maria

17:40 Particle-flow reconstruction with Transformer

Transformers are one of the recent big achievements of machine learning, which enables realistic communication on natural language processing such as ChatGPT, as well as being applied to many other fields such as image processing. The basic concept of a Transformer is to learn relation between two objects by an attention mechanism. This structure is especially efficient with large input samples and large number of learnable parameters.
We are studying this architecture applied to the particle flow, which reconstructs particles by clustering hits at highly-segmented calorimeters and assign charged tracks to the clusters.
We apply the structure inspired from a translation task, which uses the Transformer as both an encoder and a decoder. An original sentence is provided to the encoder input leading to a translated sentence as output of the decoder. The latter is initially provided with a start token and then recursively uses its own output as inputs to obtain the final translated sentence.
We supply hits and tracks to the encoder as input, and a start token to the decoder to obtain the first cluster. Truth clusters information are provided at learning stage to compare with the decoder output.
Detailed implementation of the network as well as initial results of particle flow reconstruction using this method will be shown in the presentation.

Speaker: Paul Wahlen (ICEPP, The University of Tokyo)

17:40 Possible effects of the composite dark matter at the linear collider

The existence of dark matter is currently one of the strong motivations for beyond the standard model. We consider the model of the composite dark matter. Our model assumes that meson-like dark matter (call it dark mesons) is a bounded state of dark quark ($\psi$) and anti-dark quark ($\bar{\psi}$) pairs, where $\psi$ and $\bar{\psi}$ have a confining force at work. Confining force is based on the QCD-like $SU(N)$ hidden color gauge theory. This dark matter sector connects to the Standard model via a real singlet scalar particle. The $SU(N)$ hidden color gauge sector in the dynamical chiral symmetry breaking generates Nambu-Goldstone bosons ($\tilde{\pi}$ dark meson) and massive composite scalar bosons ($\tilde{\sigma}$ dark meson) simultaneously. A real singlet scalar particle gives the current mass for the dark quark. The current mass for dark quark breaks explicitly chiral symmetry. Nambu-Goldstone bosons are massive, meaning they are dark matter candidates. We use an effective theory for dark matter interactions in the framework of the linear sigma model. In the dark mesons of $SU(N)$ hidden color, the chiral partner of the $\tilde{\pi}$ meson is the $\tilde{\sigma}$ meson (iso scalar-scalar). $\tilde{\sigma}$ is also a candidate as dark matter. We will investigate the missing energy for the final state of our model at HL-LHC and the future linear collider.

Speaker: Yuko Murakami (Hiroshima University)

17:40 Possible excess of the multi-lepton signal from dark Higgs

Recently, CMS group shows the data of the multi-muon signals. Two years ago, possible excess of dimuon signal was reported in Moriond 2023. This year, four muon signal is reported in Moriond 2024. Both data indicates the excess level of $2\sigma$. It is possible that these excesses are from Hidden sector physics. We consider the way to account for the excesses by setting SM and 2 dark sector. In the future Higgs factory, our scenario is expected to be tested by the event reconstruction in clean environment.

Speaker: Dan Kondo

17:40 R&D of the EM Calorimeter Energy Calibration with Machine Learning based on the low-level features of the Cluster

We have developed the energy calibration method by using the machine learning for the ILC EM calorimeter (ECAL), a sampling calorimeter consisting with Silicon-Tungsten layers.
In this method, we use deep neural network (DNN) to get the energy of the incident particle (energy calibration), as a regression problem,
to improve the energy calibration resolution of ECAL.
We have developed the DNN architecture where cluster hit data are input as low-level features of the cluster.
We'll report the status of the R&D.

Speaker: Suzuna Morimasa (Osaka Metropolitan University)

17:40 ScandiNova modulators for electron-driven positron source in ILC project

The International Linear Collider (ILC) is an electron-positron linear collider to explore physics beyond the Standard Model of particle physics in the center of mass energy of 250 GeV to 1 TeV.
In the TDR, to make a positron, a helical undulator of more than 150 m long will be planning to insert in the main electron linac.
And in parallel, to mitigate the risks associated with the project, a backup system by using electron-driven positron source has been studying. In this paper, we will describe the solid state modulator with klystron, called "RF unit", which maybe possible to realize the ILC positron source.

Speakers: Osamu Yushiro (ScandiNova Systems KK), Mr kevin Pepitone (ScandiNova Systems AB)

17:40 Study of Majorana Right Handed Neutrino (RHN) production at ILC

We study Majorana Right Handed Neutrinos (RHN) production at ILC. Various extensions of the SM aim to explain the origin of the tiny neutrino mass; one of them is by the introduction of RHN. When we assume that RHN is a Majorana particle, RHN pair production is allowed in e−e+ collisions. We focus on this RHN pair production based on a minimal U(1)B−L model. A distinctive signature is a pair of same sign leptons, which is almost free of SM backgrounds.
In our study, we used full detector simulation to analyze RHN production at ILC. We generated this process, investigated its properties, developed reconstruction and selection strategies and evaluated the sensitivity at ILC. Considering full SM backgrounds, we derived exclusion limits on minimal U(1)B−L parameters at ILC.

Speaker: Jurina Nakajima (SOKENDAI/KEK)

17:40 W pair production at lepton colliders in the Feynman Diagram gauge

We study the W pair production at future lepton colliders. For the production of longitudinally polarized W bosons, it is well known that large gauge cancellation occurs among the amplitudes, especially at high energies, because of the energy growth of each amplitude. In this study, we adopt a recently-proposed gauge fixing, so-called Feynman-Diagram gauge and revisit the process to show such energy growth is absent in the FD gauge.

Speaker: Hiroyuki Furusato (Iwate University)

17:40 WIMP search at future lepton collider

Minimal dark matter is one of the most motivated dark matter candidates, and many analyses at collider experiments for this model have been discussed. In our work, we considered the search for minimal dark matter at future high-energy lepton collider experiments. We found that the indirect search, which measures the quantum correction to the muon elastic scattering, is much more sensitive than the direct search. We also discussed the usefulness of the polarised muon beam in this search.

Speaker: Atsuya Niki (University of Tokyo)

18:00 On the PMNS matrix: symmetry and non-unitarity

Neutrino oscillation is a phenomenon where the neutrino oscillates between its flavor states while propagating. This comes as a result of neutrino flavor states being eigenstates of the weak interaction Hamiltonian but not of the propagation Hamiltonian. The latter possesses different eigenstates called the mass states. The change of basis between these states is described by a unitary matrix called the PMNS matrix. The PMNS matrix can be parametrized by three mixing angles and a CP violation phase. In this project we discuss two different aspects of this matrix: symmetry and non-unitarity. The symmetry aspect refers to the existence of a certain pattern within the oscillation parameters. The non-unitarity part in its turn aims at assessing the unitarity of the PMNS matrix providing an indirect search for sterile neutrinos. We endeavor to implement and assess these aspects using the P-theta framework developed by the T2K collaboration. This latter integrates the systematic parameters of T2K and HK with oscillation parameters in order to give predictions to be compared with data.

Speakers: Mr Ahmed Chahlaoui (ICRR, The University of Tokyo), Mr Aymane Maaitat (ICRR, The University of Tokyo)

18:20 AWAKE: from proof-of-concept towards first particle-physics applications

The AWAKE project at CERN makes use of plasma to transfer energy from the SPS proton beam to a short witness beam of electrons. We here give an overview of the project, from the exploitation of beam-plasma instabilities to generate large accelerating fields, to the next stages of the project, which will demonstrate sustained accelerating gradients and control of the witness bunch emittance. These developments will allow the first applications of AWAKE-like technology to particle physics in the 2030s.

Speaker: John Patrick Farmer (Max Planck Society (DE))

Tuesday, 9 July

09:00 → 10:40 Advanced Accelerator Concepts: 1

09:00 Physics Considerations for 10-30 TeV e+e-, γγ, and μ+μ- Colliders

After the program of Higgs boson physics at a linear collider is completed, we expect that the long, straight tunnel can be used with advanced acceleration methods, such as plasma wakefield, to create a higher-energy collider in the 10's of TeV CM region. This might be an e+e- or a γγ collider. (Circular) muon colliders are also discussed for this energy regime. I will discuss the physics goals of these machines, the luminosity requirements, and the trade-offs among the μ+μ-, e+e-, and γγ options.

Speaker: Michael Peskin

09:20 Luminosity Spectra of Multi-TeV PWFA Gamma-Gamma Colliders

There is growing interest in the gamma-gamma configurations of multi-TeV PWFA colliders since they do not require positrons or flat beams and may have the same particle physics potential as multi-TeV electron positron or muon anti-muon colliders. In this report the CAIN Monte Carlo is used to study the luminosity spectra of several gamma-gamma configurations assuming a round beam 15 TeV PWFA electron electron collider with a geometric luminosity of 1.5e36 cm-2 s-1. As a starting point, the parameters for optical laser and X-ray laser gamma gamma Higgs factory designs are scaled to 15 TeV center-of-mass energy. Wide variations in the luminosity spectra are observed as the laser wavelength is varied. Large beam-beam electromagnetic fields strengths – approaching 60% of the Schwinger field in some cases – play a major role in determining the size and shape of the gamma-gamma luminosity spectra.

Speaker: Tim Barklow (SLAC National Accelerator Laboratory (US))

09:40 Preliminary Investigation of a Higgs Factory based on Proton-Driven Plasma Wakefield Acceleration

A Higgs Factory is considered the highest priority next collider project by the high-energy physics community. Very advanced designs based on radio-frequency cavities exist, and variations on this approach are still being developed. Recently, also an option based on electron-bunch driven plasma wakefield acceleration has been proposed. In this article, we discuss a further option based on proton-driven plasma wakefield acceleration. This option has significant potential advantages due to the high energy of the plasma wakefield driver, simplifying the plasma acceleration stage, and due to the breadth of particle physics research it will make possible. Its success will depend on further developments in producing compact high-energy proton bunches at a high rate.

Speaker: John Patrick Farmer (Max Planck Society (DE))

10:00 Betatron radiation diagnostic systems for a plasma wakefield-based linear collider

Characterizing the beam-plasma interaction in the plasma wakefield accelerator, an essential ingredient for a potential linear collider or free-electron laser represents a significant challenge for experimental measurements. The typical dimensions involved in such diagnostic systems are below one micron, with attendant femtosecond time-resolution. Further, the plasma environment and the beam intensity generally prevent insertable, destructive diagnostics. The most robust window into this interaction is betatron radiation, which reveals beam properties such as size, emittance, matching, and development of instabilities. In this talk, we review the powerful new double-differential spectrometer under development at UCLA that is to be installed at FACET-II. We discuss the unique optics of this Compton-based spectrometer, which permits single shot measurements of incoming betatron gamma spectra ranging from 0.2 to 30 MeV. We describe significant progress in implementing machine learning techniques for reconstructing the beam-plasma interaction physics.

Speaker: James Rosenzweig (UCLA)

10:20 HALHF: Current Status, Optimisation, and Future Plans

The HALHF concept utilises beam-driven plasma-wakefield acceleration to accelerate electrons to very high energy and collide them with much lower-energy positrons accelerated in a conventional RF linac. This idea, which avoids difficulties in the plasma acceleration of positrons, has been used to design a Higgs factory that is much smaller, cheaper, and greener than any based solely on radio-frequency technology. The talk will outline the original HALHF design, discuss challenges to that design put forth by the HALHF collaboration and wider community, and highlight the optimisation process pursued to solve these challenges. Finally the current status of the design—including possible evolution in several parameters—and plans for the next steps towards a pre-Conceptual Design Report and the next ESPP Update will be given.

Speaker: Richard D'Arcy (University of Oxford)

09:00 → 10:30 BSM, Global Interpretations: 1

09:00 Status of BSM searches at ATLAS including some future prospects at HL-LHC

Despite successfully predicting the outcome of hundreds of measurements at colliders and other experiments, the standard model of particle physics cannot be the final theory of nature. Searches for beyond-the-standard model (BSM) physics are now a major component of the research program at the ATLAS and CMS experiments at the Large Hadron Collider (LHC). This talk presents highlights of BSM searches at the LHC, including dark matter, long-lived particles, heavy resonances, leptoquarks, supersymmetric particles, BSM decays of SM particles, and other exotic phenomena. Experimental methodologies, sophisticated analysis tools including machine learning, experimental results, and phenomenological interpretations including Effective Field Theories are presented.

Speaker: Caterina Vernieri (SLAC National Accelerator Laboratory (US))

09:25 Consistent excesses in SUSY searches at the LHC: Physics case for a Linear Collider

Recently ATLAS and CMS published search results in the search for SUSY particle production channel $pp \to \tilde\chi_2^0 \tilde\chi^\pm_1$ in three different final states ($3l$, $2l$ and mono-jet). All searches in both experiments show consistent (small) excesses for $m_{\tilde\chi^0_2} \approx m_{\tilde\chi^\pm_1} \approx m_{\tilde\chi^0_1} + 20$ GeV. We discuss these excesses and their implications for an $e^+e^-$ collider operating at an energy of 500 GeV.

Speaker: Sven Heinemeyer (Consejo Superior de Investigaciones Cientificas (CSIC) (ES))

09:45 "Here be SUSY" - Prospects for SUSY searches at future colliders

Some say SUSY is dead, because LHC has not discovered it yet. But is this
really true? It turns out that the story is more subtle. SUSY can be 'just
around the corner', even if no signs of it has been found and a closer
look is needed to quantify the impact of LHC limits and their implications
for future colliders. Here, a scan of the relevant parameter space of
(weak-scale) SUSY parameters, is presented.

I concentrate on properties relevant to evaluate the experimental
prospects: mass differences, lifetimes and decay-modes. The observations are
then confronted with estimated experimental capabilities.

I have considered what can be expected from (HL-)LHC, where it
turns that large swaths of SUSY parameter space will be hard to access.
For e+e- colliders, the situation is simple:
at such colliders, SUSY will be either discovered or excluded almost to
the kinematic limit.

Speaker: Mikael Berggren (Deutsches Elektronen-Synchrotron (DE))

10:05 Stau searches at future e+e- colliders

The future e+e- colliders offer excellent facilities for SUSY searches. The stau, superpartner of the tau-lepton, is one of the most interesting particles for these searches, being likely the lightest of the sfermions, first one that could be observed, and it can be regarded as the worst and thus most general scenario for the searches.
The prospects for discovering stau-pair production at future e+e- factories and the resulting detector requirements will be discussed. The study takes the ILD detector concept and ILC parameters at 500 GeV as example. It includes all SM as well as beam induced backgrounds. It shows that with the chosen accelerator and detector conditions, SUSY will be discovered if the NLSP mass is up to just a few GeV below the kinematic limit of the collider.
Expectations for another accelerator and detectors conditions are derived. In particular the role of the hermeticity of the detector and of the ability to operate trigger-less will be discussed.

Speaker: Mikael Berggren (Deutsches Elektronen-Synchrotron (DE))

09:00 → 10:30 Calorimetry, Muon detectors: 1

09:00 Addressing technological challenges on sensor-electronics hybridization for compact silicon tungsten electromagnetic calorimeters.

Highly compact and granular sandwich silicon tungsten calorimeters are part of the detector concepts proposed for all future Higgs Factories and for strong-field-QED (LUXE) or Dark Matter search experiments. This contribution discusses some of the technological challenges of sensor-electronics hybridization for this type of calorimeters. Different alternatives have been explored and used in the past, e.g. tab-bonding and epoxy-silver glue dots, with limited success. A joint R&D effort by different groups to study this technology's long-term viability. It comprises ageing studies, careful monitoring of PCB mechanical properties, the validation of different industrial choices for the epoxy-silver product and the optimization/automation of the process by different institutes. The challenges and status of these activities are discussed in this contribution.

Speaker: Adrian Irles (IFIC (CSIC/UV) Valencia)

09:30 Excellent time resolution and high rate capable Cherenkov detector for next-generation calorimetry

Several future collider experiments are proposed for precise measurement of Higgs that require calorimeter technology with excellent jet energy resolution. To fulfill the requirement, this study aims to develop next-generation calorimetry that combines "particle flow calorimetry" and "dual-readout calorimetry". For the aspect of particle flow calorimetry, highly segmented readouts are implemented in the active layers. At the same time, for the aspect of dual-readout calorimetry, two different kinds of signal generation: scintillation and Cherenkov radiation are used to improve energy reconstruction for hadrons. This study also turns the spotlight on the timing measurement of the calorimeter. It is to establish a detector technology of picosecond-level time resolution for a large detection area and to investigate the impact of timing information as additional input for particle flow or cut for background reduction. As a result, the proposed calorimetry precisely measures not only energy but also position and timing and opens access to the "5D calorimeter".
To realize such a concept, a Cherenkov detector with highly segmented readouts and picosecond-level timing resolution that can cover a large area is required. Cherenkov light generated by charged particles is converted to photoelectrons by a photocathode and subsequently amplified by the Resistive Plate Chamber (RPC) is one candidate for such a detector. Notably, the amplification layer utilizes an RPC with a Diamond-like Carbon (DLC) electrode, providing high-rate capability overcoming the conventional drawbacks of RPCs.
This presentation describes the demonstration of the detector concept of the Cherenkov detector.

Speaker: Weiyuan Li (The University of Tokyo)

10:00 Photon and Electron Reconstruction in an Ultra-High Granularity Luminosity Calorimeter

Our recent work has shown that a novel, ultra-high granularity,
forward calorimetry concept can enable much more detailed and precise
reconstruction than the compact baseline designs based on LEP luminometers, together
with the capability of electron/positron/photon separation.
In this contribution we will highlight the significantly more precise
measurements of photon four-vectors using both much better sampling for
high performance energy resolution (4%/$\sqrt{E}$) and the use of the energy deposition
around the initial photon conversion point rather than the traditional shower
center-of-gravity based estimates. We will also include related results on shower fitting.

Speaker: Brendon Madison (University of Kansas)

09:00 → 10:30 Higgs, Electroweak: 1

09:00 Higgs measurements at the LHC and HL-LHC (Invited)

Invited talk on Higgs measurements at the LHC and HL-LHC

Speaker: Dengfeng Zhang (University of Sheffield (GB))

09:30 Determination of CP-violating Higgs couplings with transversely-polarized beams at the ILC

We study possible CP-violation effects of the Higgs to $Z$-boson coupling
at a future $e^+ e^-$ collider, e.g. the International Linear Collider (ILC). We find that the azimuthal angular distribution of the muon pair, produced by $e^+ e^- \rightarrow H Z -> H \mu^+ \mu^-$, can be sensitive to such a CP-violation effect when we apply initial transversely polarized beams. Based on this angular distribution, we construct a CP sensitive asymmetry and obtain this asymmetry by Whizard simulation. By comparing the SM prediction with 2$\sigma$ range of this asymmetry, we estimate the limit of the CP-odd coupling in $HZZ$ interaction, including as well studies from unpolarized and longitudinally-polarized beams.

Speaker: Dr Cheng Li (Sun-Yat-Sen University)

09:50 Prospects of measuring quantum entanglement in H->tautau at a future e+e- Higgs factory

Final states with spin-correlations allow the measurement of quantum entanglement at collider energies. The $H\to\tau\tau$ process is an excellent probe for this, due to the scalar nature of the Higgs boson, and the direct access to the $\tau$-lepton helicity through the angular distributions of the $\tau$-lepton decay products. We will present the prospects of such a measurement a future $e^+e^-$ Higgs factory using Delphes simulation samples for the signal and the relevant background processes. The construction of observables sensitive to quantum entanglement of the $\tau$-$\tau$ system will be discussed together with the impact of reconstruction and event selection effects on the sensitivity.

Speaker: Mr Cedric Breuning (University of Bonn)

10:10 Decoding Higgs Boson Branching Ratios from Event Shape Variables

In this talk I will discuss a novel strategy [1] for the simultaneous measurement of Higgs-boson branching ratios into gluons and light quarks at a future lepton collider operating in the Higgs-factory mode. The method is based on template fits to global event-shape observables, and in particular fractional energy correlations, thereby exploiting differences in the QCD radiation patterns of quarks and gluons. This is
orthogonal to measurements based on traditional tagging methods based mainly on displaced vertices and allows for an extraction of limits on both Higgs boson to gluon- and light quark branching ratios separately. I will also comment on state of the art calculations for the relevant observables based on [2].

[1] Eur.Phys.J.C 84 (2024) 1, 83
[2] arXiv:2403.06929

Speaker: Daniel Reichelt

09:00 → 10:30 Sources: 1

09:00 Positron source for CEPC

The CEPC Linac is a normal conducting S-band and C-band combined Linac providing electron and positron beams at an energy up to 30 GeV with 100 Hz repetition. The positron source of CEPC adopts a conventional scheme, electron beam energy on the target is 4GeV with a 10nC bunch charge. This talk will introduce the design of CEPC positron sources, including positron generation, capture, pre-acceleration, and the positron damping ring. The development of key components such as a flux concentrator and its solid-state modulator for CEPC positron source will be discussed. Other research activities related to CEPC sources will also be mentioned.

Speaker: Xiaoping Li (Institute of High Energy Physics, IHEP)

09:20 Update on Ce+BAF Positron Activities

A baseline concept for a continuous wave (CW) polarized positron injector was developed for the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (Ce+BAF) [1]. This concept is based on positron beam generation by a high current polarized electron beam (1 mA, 120 MeV, 90% polarization) irradiating a water-cooled, 4 mm thick rotating tungsten target or suitable alternative. An overview of the Ce+BAF concept and update about the positron injector development activities will be presented, including the polarized electron source concept, simulations of positron beam generation, positron capture, calculations of energy deposited by beams in the target, capture magnets and standing wave cavities, and shielding design.

[1] J. Grames et al., "Status of Ce+BAF: Polarized Positron Beam Capability at CEBAF 12 GeV", 14th International Particle Accelerator Conference (IPAC'23), Venice Italy, May 7-12, MOPL152.

Speaker: Andriy Ushakov (Jefferson Lab)

09:40 SuperKEKB positron beam tuning using ML

In the KEK Injector Linac, four-ring simultaneous injection has been achieved, and beam tuning is always performed in various beam modes. The beam tuning is complicated with many tuning knobs. We have developed an automatic tuning tool, which is realized by using Bayesian optimization and the downhill simplex method. It was especially useful in positron generation. I will report on the implementation of the automatic tuning and some test results.

Speaker: Takuya Natsui (KEK)

10:00 The positron source of STCF in China

The proposal for a new generation high-luminosity electron-positron collider, the Super Tau-Charm Facility (STCF), has been put forward in China. The STCF is expected to achieve a luminosity greater than 0.5×1035 cm-2 s-1 and operate within a center-of-mass energy range of 2 to 7 GeV. Considering the design challenges of the STCF collider ring, swap-out injection has been suggested as one of the alternative injection methods to achieve the desired luminosity. Therefore, the STCF injector will investigate both off-axis injection and swap-out injection methods concurrently. The demand for positron injection charge under swap-out injection is much higher than that of off-axis injection, requiring at least 300nC/s positron injection. Two positron source designs for both off-axis and off-axis injection will be presented in this paper.

Speaker: Ailin Zhang (University of Science and Technology of China)

09:00 → 10:30 Superconducting RF: 1

Convener: Enrico Cenni

09:00 Oxide dissolution and oxygen diffusion scenarios in niobium and implications on the Bean–Livingston barrier in superconducting cavities

We generalize a native Nb2O5 dissolution model [G. Ciovati, Appl. Phys. Lett. 89, 022507 (2006)] to sequential overlayer dissolutions, multilayer dissolution, and realistic temperature profiles, which may be applicable to other materials. The model is applied to secondary ion mass spectrometry depth profile measurements for varying temperature profiles and two-step oxide dissolution in Nb and found to agree well. In the context of the Meissner screening response due to impurity profiles on the length scale of the London penetration depth, the shallow diffusion of O impurities results in a substantial decrease in the peak supercurrent density near the surface. In this framework, oxide dissolution and oxygen diffusion can account for a rise in peak supportable magnetic field in SRF cavities with baking time and a suppression after the optimal baking time is reached, in good agreement with peak-field baking temperatures and times as well as recent quench field measurements.

Speaker: Eric Lechner (Thomas Jefferson National Accelerator Facility)

09:20 SRF programs towards High-Q/High-G cavities in IJCLab

IJCLab has been leading development and deployment of low-beta SRF cavities for proton and heavy ion accelerators.
We are launching a new project for sustainable Energy Recovery Linac (iSAS/PERLE) with state-of-the-art SRF cavities at 800 MHz.
Our proposal includes advanced heat treatment of such cavities to reach excellent quality factor at high fields.
In this talk, we overview the status of this activity and its technical synergy with other SRF projects, such as FCCee, EIC, and ILC.

Speaker: Akira Miyazaki (CNRS/IN2P3/IJCLab Université Paris-Saclay (FR))

09:40 Status of fabrication of 9-cell cavities.

We have the Cavity Fabrication Facility (CFF) at KEK. This facility was constructed to focus on the fabrication of SRF Nb cavities. Recently we fabricated one FG-Nb 9-cell cavity which complies with High Pressure Gas Safety code at CFF/KEK. We also are fabricating a 9-cell cavity with new Nb material, Medium-Grain (MG) Nb, which has the Nb grain size of sub-mm. The presentation reports the status of fabrication of 9-cell cavities at CFF/KEK.

Speaker: Takayuki SAEKI (KEK)

10:00 sX mapping system test at ORNL

The Kyoto-KEK sX mapping system was applied to the vertical testing of a 805 MHz 6-cell SNS high-beta cavity (HB60) aimed at localizing field emitters in the cavity. The test result will be presented and implication to the on-going effort in the battle against field emission in current and future SRF cavities will be discussed.

Speaker: Rongli Geng (Jefferson Lab)

10:30 → 11:00 coffee

11:00 → 12:30 Conventional Facilities, Machine Detector interface: 1

11:00 IP-BDS area sub-tunnel proposal and progress of the 3D CAD models of ILC

The proposed sub-tunnels are considered necessary for the construction, installation and operation of the BDS and beam dump. It would also provide access to facilities such as a laser room for polarimetry, a preparation room for beam dump experiments and magnet power supply rooms.
A constantly updated 3D CAD model will also be presented.

Speaker: Dr Nobuhiro Terunuma (KEK)

11:20 Study on the development schedule for the central area of the ILC in Kitakami

The development schedule of the ILC Central Area affects the assembly and installation schedule of the detectors, which in turn significantly impacts the overall ILC construction schedule. We conducted a detailed study of the process required for constructing the ILC at the Kitakami site in Japan, from the start of construction until the assembly of detectors can be started. The results of this study will be reported.

Speaker: Tomoyuki Sanuki (Tohoku University)

11:35 On site magnet winding

On site magnet winding

Speaker: Yasuhiro Makida (KEK)

11:50 News on big solenoids

News on big solenoids

Speakers: Karsten Buesser (DESY), Karsten Roland Buesser (Deutsches Elektronen-Synchrotron (DE))

12:05 Belle II IP Chamber

Belle II IP Chamber

Speaker: Mr Kyo Shibata (KEK)

11:00 → 12:30 Damping rings, Beam delivery systems: 1

Convener: Andrea Latina (CERN)

11:00 ATF2 status and operation 2023-2024

ATF2 status and operation 2023-2024 will be presented.

Speaker: Alexander Aryshev (KEK)

11:15 Wakefield study at ATF2 beamline

Wakefield study at ATF2 beamline will be presented.

Speaker: Dr Yuki Abe (KEK)

11:30 KEK ATF Linac and Damping Ring klystrons High-Power RF field phase and amplitude stability study

KEK ATF Linac and Damping Ring klystrons High-Power RF field phase will be presented.

Speaker: Dr Konstantin Popov (KEK)

11:45 Ultra-low Beta* experimental studies at ATF2 and future plans

Ultra-low Beta* experimental studies at ATF2 and future plans will be presented.

Speaker: Mr Andrii Pastushenko (CERN)

12:00 ILC C-BPMs status and plans

ILC C-BPMs status and plans will be presented.

Speaker: Laura Karina Pedraza Motavita (IFIC (Universidad de Valencia - CSIC))

11:00 → 12:30 Higgs, Electroweak: joint with BSM/GI

11:00 Collider Tests of Nanohertz Gravitational Waves

Recently, compelling evidence of nanohertz gravitational waves is indicated by the pulsar timing array collaborations. In this talk, I will present an MeV-scale first-order phase transition from a minimal dark sector to explain the gravitation waves, with a focus on the collider tests via a minimal Higgs portal. I will demonstrate that to explain the observed gravitational waves, the Higgs portal coupling should be so sizable that it can be probed through Higgs invisible decay at the LHC and future lepton colliders such as CEPC, ILC, and FCC-ee. It opens up a promising avenue to uncover the physical origin of the nanohertz GWs via colliders and to hear and see the minimal dark.

Speaker: Dr Shaoping Li (Osaka U.)

11:15 Searching for heavy neutral leptons in electron positron colliders

The origin of neutrino mass is a long standing puzzle. Plethora of models have been proposed to explain the origin of small neutrino mass. Among them tree level seesaw and inverse seesaw scenarios are the simplest ones where Standard Model (SM) is extended by SM-singlet heavy Right Handed Neutrinos (RHNs). If the RHN masses are $\mathcal{O}$(TeV) scale, they could be produced in lepton colliders through the mixing between the light-heavy neutrino mixing $(|V_{\ell N}|^2)$ depending on the center of mass energy. Such RHNs can decay into a variety of models involving leptons and jets. Studying such finals states from the RHNs we will show the projected bounds on the plane containing $|V_{\ell N}|^2$ and the mass of the RHN and compare with existing bounds.

Speaker: Arindam Das

11:30 Testing the gauged U(1)B-L model for loop induced neutrino mass with dark matter at future colliders

We present a new viable benchmark scenario under the current experimental data for the model which can explain the tiny mass of active neutrinos and dark matter. Majorana masses of right handed neutrinos are given by the spontaneous breaking of the U(1)B-L gauge symmetry at the TeV scale, and tiny neutrino mass are radiatively induced by quantum effects of particles of the dark sector including the dark matter candidates. We first show the benchmark points which satisfy current experimental data, and then discuss how this model can be tested at future experiments including electron-position linear colliders.

Speaker: GUOHAO YING (Osaka University)

11:45 Higgs Production at \mu^+ \mu^+ Colliders

Muon colliders offer exciting new opportunities to explore the Standard Model and beyond by unifying the energy and precision frontiers, thus also facilitating deeper insight into the Higgs sector central to the Standard Model. In this work, motivated by recent developments in anti-muon cooling, we explore the prospects of Higgs production at \mu^+ \mu^+ colliders. At high energies, Higgs production is dominated by WW-fusion, which for \mu^+ \mu^+ colliders occurs via splitting of an intermediate photon into a W^+ W^- pair. However, collinear photon emissions lead to numerical instabilities that make computations using event generators difficult. We therefore propose splitting the phase-space into the sum of a non-collinear region calculable using event generators, and a collinear region approximated by a parton distribution function for the photon. We thus find that the cross-section for Higgs-production at \mu^+ \mu^+ colliders is almost as big as for \mu^+ \mu^- colliders, and in particular for polarized anti-muons, is only smaller by a factor of about two. Hence, we argue that \mu^+ \mu^+ colliders offer a great opportunity as Higgs factories to be constructed in the not-too-distant future.

Speaker: Mr Lukas Treuer (KEK, The Gaduate U. Adv. Studies (SOKENDAI))

12:00 Exploring new physics by loop-corrected decays of additional Higgs bosons

In order to test and discriminate the extended Higgs models, it is quite important to include radiative corrections to the analyses for the synergy between the precise measurements of the discovered Higgs boson (h125) and the direct searches for additional Higgs bosons. Deviations of couplings of h125 from the standard model (SM) predictions give the upper limit on masses of additional Higgs bosons, and change predictions of decay rates of additional Higgs bosons. Precise calculations including loop corrections are clearly important for comparison with precise measurements of the h125 couplings in future collider experiments. We calculate the loop-corrected correlation between the branching ratio of additional Higgs bosons and the deviation in the h125 → ZZ∗ decay from the SM prediction in the two Higgs doublet model,
and show that loop corrections can significantly change the correlation predicted at LO. We perform the calculations of loop corrections based on Fortran code "H-COUP version 3" (http://www-het.phys.sci.osaka-u.ac.jp/~hcoup/) with some modifications for the renormalization conditions.

Speaker: Mariko KIKUCHI (Nihon University)

12:15 $4b +X$ via electroweak multi-Higgs production as smoking gun signal for the Type-I 2HDM at the LHC

The existence of additional Higgs bosons, besides the one
discovered by the LHC, already a decade ago, is predicted by most
frameworks of new physics. Observation of a second Higgs boson
(charged or neutral) will thus provide a firm evidence that the
underlying manifestation of the Electroweak Symmetry Breaking (EWSB)
mechanism is a non-minimal one. The majority of analyses, both
phenomenological and experimental ones, involving additional Higgs
bosons concentrate on QCD induced production modes.
However, the QCD induced processes are not necessarily to be high in
new physics models owing to the non-standard couplings of the
new Higgs bosons to the fermions and gauge bosons. As a reference,
I consider the Type-I two Higgs doublet model (2HDM) as a simple
extension of Standard Model where the Electroweak (EW) processes dominate
over the QCD processes. I would like to discuss a full detector-level Monte Carlo analysis to establish that the inclusive $4b+X$ final state via EW processes can provide simultaneous reconstruction of all the additional Higgs boson masses. I will present the algorithms for the mass reconstructions of the additional Higgs bosons.

Speaker: Dr Prasenjit Sanyal (Konkuk University)

11:00 → 12:30 Normal conducting RF: 1

11:00 X-LAB: A VERY HIGH-CAPACITY X-BAND RF TEST STAND FACILITY AT THE UNIVERSITY OF MELBOURNE

The first Southern Hemisphere X-band Laboratory for Accelerators and Beams (X-LAB) has been commissioned at the University of Melbourne. One of the key projects within this laboratory involves repurposing half of the CERN X-band test stand XBOX3, now known as Mel-BOX.
This initiative aims to validate the performance of high-gradient travelling wave accelerating structures, crucial for the Compact Linear Collider (CLIC) beam-based acceleration baseline, operating at a frequency of 12 GHz.
To assess the structures' performance under high peak power and short pulse width RF conditions, two klystron-based test facilities have been operationalised for this year. Similar to XBOX3, Mel-BOX adopts an innovative approach to combine high average power klystron units, facilitating power distribution to two testing slots with a repetition rate of up to 400 Hz. Additionally, the parameters such as repetition rate, peak power, pulse length, and pulse shape can be tailored to meet specific testing requirements. This novel method of generating high-power, high-repetition RF pulses holds promise for various applications necessitating multiple test slots.
Moreover, there are plans to leverage this technology as a foundation for developing compact accelerators tailored for medical or university applications, including radiotherapy and compact light sources.

Speaker: Matteo Volpi (University of Melbourne (AU))

11:20 X-band activities for the EuPRAXIA@SPARC_LAB Linac

Over recent years, significant efforts have been dedicated to validating the reliability and functionality of X-band technology at extremely high peak fields and accelerating gradients to achieve the realization of increasingly compact linacs. The Eupraxia@SPARC_LAB project entails the development of 1GeV Linac utilizing a X-band booster comprising 16 accelerating structures operating at a nominal gradient of 60MV/m. At the Frascati laboratories of INFN (LNF) in the last year various X-band RF components essential for the Eupraxia Linac have been developed and have been tested at nominal peak power conditions. This was made possible thanks to the use of the TEX test facility devoted specifically for the development and testing of RF devices and accelerating structures in the X-band. Recently, the first RF prototype of X-band accelerating structure designed at LNF has been manufactured and tested at high power. This report presents the results of the latest tests conducted at TEX and the preliminary results of the conditioning of the first accelerating structure prototype for the EuPRAXIA@SPARC_LAB project.

Speaker: Fabio Cardelli

11:40 Smartcell X-Band Normal Conducting Accelerator Structure Prototype Fabrication

This presentation details the design and fabrication process of a prototype of a normal-conducting X-band accelerator structure, which we denominate Smartcell. These structures, achieved through brazing/bonding techniques, are crucial components for future linear colliders.
We will cover the brazing/bonding geometry, materials selection and their implications, variations in heat cycles, and atmospheres employed during brazing/bonding. The impact of copper quality and annealing procedures implemented before, during, and after machining will be discussed specifically on how they can influence the machinability, microstructure, and ultimately the performance of the final component.
The presentation will showcase the behaviour of five mock-ups, including the results and conclusions obtained through optical examination, metrology, and SEM analysis. We will also discuss silicon carbide RF properties and characterization throughout the fabrication process.

Speaker: Pedro Morales Sanchez (CERN)

12:00 X-band dielectric assist accelerating structure.

A dielectric assist accelerating (DAA) structure, which consists special dielectric cell structures operating in the TM02n mode, is greatly superior in power efficiency compared with the conventional normal conducting copper structures. On the other hand, DAA structures stays at a low achievable accelerating gradient due to multipactor and breakdowns. To overcome these problems, we try to develop X-band standing-wave DAA structures and work to understand the physics of the breakdown phenomena occurring inside them.

A two-cell DAA structure composed by sapphire cell structures has been developed. The unloaded Q was measured to be above 60,000 at room temperature, in good agreement with the simulation results. This DAA structure is to be tested using the X-band high power test facility, Nextef2 at KEK. In the high-power test, we plan to perform a short pulse RF excitation using step pulse input in DAA structures to verify the potential of them to generate a high accelerating field. In this conference, we will present the status and progress in the development of the X-band DAA structure.

Speaker: Daisuke Satoh (National Institute of Advanced Industrial Science and Technology (AIST))

11:00 → 12:30 Superconducting RF: 2

Convener: Yasuchika Yamamoto (KEK)

11:00 Cavity tuner development for the ITN cryomodule at KEK

In this contribution we report on the development of a cavity tuner for a cryomodule, which is being developed and will be built and tested in the scope of the International Linear Collider (ILC) Technology Network (ITN) at KEK until 2027. We have simulated Lorentz-force detuning of the according SRF 1.3 GHz 9-cell TESLA-type cavities to understand the tuner requirements better. As a base of the ITN cavity tuner design the LCLS-II double-lever tuner was selected. In a collaboration with Fermilab we have tested the LCLS-II tuner on an LCLS-II cavity at room temperature and atmospheric pressure. Based on the gained experience, design adjustments are being considered. Slow and fast tuner driving electronics were partially selected.

Speaker: Dr Mathieu Omet (High Energy Accelerator Research Organization (KEK))

11:20 Production status of power coupler in MEXT-ATD/ITN

At KEK, from FY2023, new 5-year plan for SRF technology development has started under MEXT-ATD program partly related to ITN. Power coupler is one of them, basically same as E-XFEL design. We chose the ceramics material developed by collaboration of KEK-KYOCERA. And, we changed some design from E-XFEL. We have done the RF simulation to evaluate the effect of these changes. In FY2024, we will produce four sets of power coupler including connecting waveguide. We will also perform necessary quality control/assurance using some samples. In this presentation, we will report the recent progress.

Speaker: Dr Ryo Katayama (KEK)

11:40 Development of the RF power distribution System for the ILC Prototype Cryomodule

The RF power distribution system for the International Linear Collider (ILC) is redesigned based on the updated requirements established in the scope of the ILC Technology Network (ITN) at KEK. Its main features are a low center of gravity, a compact design, and a reduced number of waveguide components. The power distribution system design is updated to avoid interference among various components in the case of future multi-cryomodule assembly. Furthermore, the concept of a local power distribution system without a circulator was introduced, which was evaluated by analytical calculations, simulations, and low-power tests. The cryomodules integrated with waveguide systems will be installed inside the tunnel. Therefore, a prototype waveguide support system was designed. A test assembly was conducted to gain a better understanding of the installation process and space requirements.

Speaker: Prakash Joshi (The Graduate University for Advanced Studies,SOKENDAI)

12:00 Cleanroom assembly of the IFMIF SRF Linac

In complement to the development activities for fusion reactors (JT-60SA & ITER), Fusion for Energy contributes to the R&D for material characterisation facilities. Within the Broader Approach agreement, different actors from Europe to Japan collaborate to develop and assemble in Japan the LIPAC, a technical demonstrator of a D+ accelerator that will be used to produce neutron by nuclear stripping reaction on a liquid Li target.
In 2024, the LIPAC is getting ready for the installation of the SRF cryomodule that will conclude its construction. Started in March 2019, the assembly was paused a first time to solve technical problems on its solenoids. Resumed in August 2022, the assembly was paused a second time after the completion of the cavity/coupler assembly to fix additional issues. In April 2024, the assembly restarted with the completion of the beam line. In this talk/paper, we will present and details the different steps of the cleanroom assembly and how the different technical difficulties were overcome.

Speaker: Janic Chambrillon (Fusion for Energy (F4E))

11:00 → 12:30 Top, QCD, Flavor, Precision Modelling: 1

11:00 The top quark EW couplings in the SMEFT

The electro-weak couplings of the top quark are directly accessible in rare "top+X" production processes at the LHC, where top quark pairs or single top quark are produced in associations with bosons. We present a new analysis of the top sector of the Standard Model EFT. The fit is based on a fully NLO parameterization and includes the most recent (differential) results from ATLAS and CMS. We show that run 2 of the LHC allows, for the first time, to overconstrain the qqttbar and two-fermion operator coefficients and yields competitive bounds. We compare the current bounds to projections for the HL-LHC and future lepton colliders, that can yield powerful constraints.

Speaker: Dr Fernando Cornet (Case Western Reserve)

11:20 Top mass measurement at the CEPC

The study is based on the publication of EPJC 83, 269 (2023).
We present a study of top quark mass measurements at the t\bar{t} threshold based on CEPC. A centre-of-mass energy scan near two times of the top mass is performed and the measurement precision of top quark mass, width and \alpha_S are evaluated using the t\bar{t} production rates. Realistic scan strategies at the threshold are discussed to maximise the sensitivity to the measurement of the top quark properties individually and simultaneously in the CEPC scenarios assuming a limited total luminosity of 100 fb^{-1}. With the optimal scan for individual property measurements, the top quark mass precision is expected to be 9 MeV, the top quark width precision is expected to be 26 MeV, and \alpha_S can be measured at a precision of 0.00039. Taking into account the uncertainties from theory, background subtraction, beam energy and luminosity spectrum, the top quark mass can be measured at a precision of 14 MeV optimistically and 34 MeV conservatively at CEPC.

Speaker: Yaquan Fang (Chinese Academy of Sciences (CN))

11:40 Top quark flavor changing neutral currents at future linear colliders

In this talk, I will discuss the potential discovery of top quark flavor changing neutral current (FCNC) at future linear colliders (LCs). First, I will discuss the theoretical predictions in a class of simplified dark matter models where the rates of top quark FCNC decays are generated by dark-sector particles. I will then discuss the sensitivity of the LCs on the top quark FCNC for some channels and some benchmark center-of-mass energies.

Speaker: Adil Jueid (Institute for Basic Science)

12:00 ttbar-threshold: Focus topics for the ECFA study on Higgs / Top / EW factories

I present the status of the ECFA Higgs/EW/Top Factory workshop activities for the ttbar-threshold focus topic (see https://arxiv.org/pdf/2401.07564).
An expert team has been setup aiming to provide a firm basis for the projected precision of the top quark mass and width measurements from a scan of the center-of-mass energy through the top quark pair production threshold. The prospects for measurements of top quark electro-weak couplings are included in the study, too. The goal is to provide a realistic estimate of statistical uncertainties, and systematic uncertainties from theory and experiment.

Speaker: Marcel Vos (IFIC (UVEG/CSIC) Valencia)

11:00 → 12:30 Vertex, Tracking, Timing detectors: 1

11:00 Nanosecond timing MAPS

The detectors at future e+e- linear colliders will need unprecedented precision on Higgs physics measurements. These ambitious physics goals translate into very challenging detector requirements on tracking and calorimetry. Monolithic Active Pixel Sensor (MAPS) technology offers small dead areas, thin sensors, and small pixels over large areas. Future e+e- Colliders could benefit from O(ns) timing tagging, with the constraint that the overall power consumption stays within the target of few tens of mW/cm^2. Today some commercial imaging technologies offer the possibility of producing large, stitched sensors (with a rectangle area ~30 cm × 10 cm). Such large sensors are very interesting from a physics point of view, but they are very challenging from an engineering point of view. A first MAPS prototype ʻNAPA-p1’was designed by SLAC in CMOS Imaging 65 nm technology. The prototype has dimensions of 1.5 mm × 1.5 mm with a pixel pitch of 25 μm. This work benefits from our collaboration with CERN, capitalizing on the improved sensor’s performance after a decade of optimizations. This prototype will set the baseline for the sensor and the electronics performance which will serve future developments. This talk will feature the first measurements performed to fully characterized this prototype.

Speaker: Caterina Vernieri (SLAC National Accelerator Laboratory (US))

11:20 DuTiP Vertex Detector for Belle II Upgrade and ILC

Belle II ugpgrade is expected around 2028 to mitigate the high background induced by electron and positron beams. We have invented a new pixel detector concept named Dual Timer Pixel (DuTiP) for the vertex detector upgrade. This pixel detector concept can be also used for the layer 7 and 8 of the ILD vertex detector. The first prototype was fabricated with lapis semiconductor 200 nm FD-SOI technology and characterization is ongoing. We will present the status and prospects of the development.

Speaker: Akimasa Ishikawa (KEK)

11:40 New TPCs with charge spreading resistive Micromegas for T2K near detector

Two new TPCs have been installed and commissioned at JPARC, as part of the upgraded T2K near detector long baseline neutrino experiment. It makes use of the ‘Encapsulated Resistive Anode Micromegas’ (ERAM) technology, developed in the last decade for the ILC TPC.
The characterization of the ERAM modules in X-ray tests, the modeling of the signal formation and of the charge spreading process, will be presented and confronted to direct surface resistivity measurements. The lessons learned for the construction and operation of an ILC TPC, and their limits, will be presented.
First event displays of the new TPCs in the JPARC neutrino beam, and performance in dE/dx and spatial resolution measured in beam tests will be shown.

Speaker: Prof. Paul Colas (Université Paris-Saclay (FR))

12:00 The Quest of Building a TPC Field Cage

For ILD, one of the detector concepts for the proposed International Linear Collider, a time projection chamber (TPC) is foreseen as the central tracking detector. The R&D effort within the LCTPC collaboration has been centred around a common infrastructure setup operated at the DESY II Test Beam Facility. This setup includes a large field cage as test bed for the different readout technologies to be studied under comparable conditions. A second iteration of this field cage has recently been constructed to improve on the shortcomings noticed with its predecessor. The construction was repeatedly delayed and interrupted due to the COVID-19 pandemic but these delays yielded insights that may not otherwise have been observed during an ordinary course of operations. Methods and findings from the build process will be reported.

Speaker: Oliver Schaefer (DESY Hamburg)

12:30 → 14:00 Lunch

13:00 → 15:30 Industry: Sustainability

13:20 AAA activities in Japan

The Advanced Accelerator Association Promoting Science & Technology (AAA) is a general incorporated association. The objective of the association shall strive in facilitating the industry-government-academia collaboration. It seeks the industrial applications of advanced accelerators and technologies with the International Linear Collider (ILC) as its core project, as well as the scientific findings in the field of particle physics. In this presentation, we will give an overview of the latest developments of activities in the Outreach, Technology Study, and the Sustainability Study groups in AAA.

Speaker: Osamu Jinnouchi (Tokyo Institute of Technology (JP))

13:35 ILC Vanguard Initiative

The ILC Vanguard Initiative was established August 2023 with the premise of situating the ILC in Japan. This includes the construction of a new social model, the creation of new values, and the materialization of the plan. The primary focus is to advance preparations for urban development related to the future and growth of the prospective site locations, which require extensive surveys, facility reviews, and careful planning. In this talk we report motivation and recent activities of the ILC Vanguard Initiative.

Speaker: Tohru Takahashi

13:50 ILC Site-Specific Activities by Tohoku ILC Project Development Center

In August 2020, Tohoku ILC Project Development Center was launched with specific studies led by the ILC region to finalize regional detailed plans for the ILC project and local decision-making issues for the construction of the ILC. This center is responsible for activities more closely related to IDT (ILC International Development Team), KEK and AAA (Advanced Accelerator Association).
The presentation includes the topographical and geological survey and the facility layout study, available sources for electrical and hydraulic power, the evaluation of the ILC central campus sites, the logistics/assembly base research/study, the urban planning and acceptance environment improvement study, the natural environment studies for the ILC siting and the green ILC.

Speaker: Atsuto Suzuki

14:05 Introduction of CEPC Industry Promotion Consortium (CIPC)

As CEPC-SppC Industrial Promotion Consortium, CIPC is an industrial collaborative organization in China that supports CEPC. It currently has nearly a hundred member units and aims to jointly tackle key technologies, cultivate industrialization, and promote the orderly development of manufacturing, technology, and engineering processes in China's industry. The report introduces the CIPC's founding background, development vision and organizational structure, details CIPC members' latest achievements in boosters, collision rings, MDI, civil engineering, cryogenics, vacuum and other CEPC related issues, comprehensively presents the CIPC's development and current situation.

Speaker: Jinlin Gao (北京中科富海低温科技有限公司)

CEPC产业促进会（CIPC）-2024.6.12-v1.pdf

14:20 Industrial Efforts for X-Band Accelerator Structure Fabrication (Europe)

Since 2007, CERN has been fabricating normal conducting structures in collaboration with industry. With PSI joining some years later, only academic institutions have been pushing for further developments of high gradient structures manufacturing in Europe.
This trend appears to be changing with growing interest from European industry, recognizing the potential of high gradient, X-band structures. Thanks to public money funding initiatives like iFast, Muhic, DEFT, XFel, Horizon 2020 with AWAKE, EuPRAXIA or Compactlight, new partnerships between research institutions and companies, have come to light enabling knowledge and technology transfer between academia and industry.
This presentation highlights the importance of this collaborative approach in overcoming the significant fabrication challenges associated with X-band structures. Specific examples of these advancements will be showcased, focusing on challenges like achieving tight tolerances on large copper structures and implementing innovative brazing techniques.

Speaker: Pedro Morales Sanchez (CERN)

14:35 Inovative Public Procurement

Innovation procurement has become a key driver on delivering solutions to social challenges that public sector is facing, including the need to modernise internal operations while delivering high quality public services.
Since 2018, Centro de Desarrollo Tecnológico y la Innovación (CDTI Innovation) has been boosting Innovation and R&D through Pre-Commercial Procurement (PCP) instrument. The aim is to close the gap of those solutions whose technology is not yet near-to-the-market but could be achieved by financing R&D activities. CDTI Innovation obtains R&D services to develop first product or service prototypes, in test serie modality, technologically innovative, and that meet public needs. The prototype developed within this framework is transferred then the Public Entity interested in the solution. To this end, Public Entities provides the needed environment for validation activities. However, the prototype will be used only as a technology demonstrator, in order to validate technology, not for commercial purposes.

Far from being a fast-track approach towards overcoming challenges, PCP instruments faces several challenges towards its stablishment as a meeting point among R&D providers, solution providers, clients and users.

Speaker: Maite del Corte Sanz

14:50 Spanish Science Industry update

Spanish Science Industry is developing technology, components systems and subsystems for particle accelerators world wide. The relationship of the industry with the scientific and technological institutes in Spain makes possible the advance of critical technologies that will be applied in the future accelerators as the International Linear Collider. During the presentation, key characteristics of Spanish Science Industry Sector and some developments related to advanced accelerators and specifically to ILC project will be presented

Speaker: Erik Fernandez (INEUSTAR)

15:05 Significance of participating in ILC-related R&D as a regional company located near an ILC candidate site

Kondo Equipment Co.Ltd. is in Kitakami City, Iwate Prefecture, where is 40-50 kilometers from the Kitakami Highlands, the candidate site of the ILC. Our company's main business is plumbing. Our main products are the piping often used in ILC, and we are able to carry out the entire process from design to construction to meet the specifications of the client. When the Kitakami Highlands are chosen as the site for the ILC, we would like to be involved in the project as a plumbing contractor and as a local company. We are currently participating in two research and development projects to make this dream a reality. One is “Design of ILC Main Beam Dump,” in which we are studying the generation of vortex flow in a water pressure vessel by using simulations in cooperation with the Iwate Prefectural Industrial Research Center and the Iwate Industrial Promotion Center under the guidance of KEK. The second theme is “Design of Cooling Water System and Piping in Electron Driven Positron Source Tunnel”. We are working on this theme with the same development structure as the first theme. We believe that local companies' participation in research to be involved in the ILC and to increase their knowledge of the ILC will contribute to and revitalize the region. As a local company, we will continue to hold this belief strongly and focus on ILC-related development and research program.

Speaker: Shinichi Takizawa

14:00 → 15:30 BSM, Global Interpretations: 2

14:20 Investigating hidden sectors at future e+e- colliders through two-particle angular correlations

Exploring long-range angular correlations among emitted particles in high-energy collisions provides an opportunity to uncover physics beyond the Standard Model like Hidden Valley (HV) models.
We focus on a hidden QCD-like sector, where the interplay between HV matter and QCD partonic cascades could enhance azimuthal correlations between final-state particles. Our investigation, performed at detector level, specifically targets the detectability of these phenomena at future e+e- colliders, yielding a cleaner experimental signature as compared to the Large Hadron Collider (LHC). Remarkably, the observation of ridge structures in the two-particle correlation function may suggest the existence of New physics.

Speaker: Emanuela Musumeci (Univ. of Valencia and CSIC (ES))

14:40 Searches for BSM physics at a gamma-gamma collider with Energy < 12 GeV based on European XFEL

The possibility of a Gamma-Gamma collider extension to the Beam
dump of the $17.5$ GeV European XFEL has been discussed before as
a first high energy collider of its sort. It would not just be to study
the concept of a gamma-gamma collider but this collider would also
be without competition in the region of $5− 12$ GeV for gamma-gamma
physics. In this range $b\bar{b}$ and $c\bar{c}$ resonances, tetraquarks as well as mesonic molecules can be observed. Furthermore some BSM processes can also be reached in this range. In this talk we want to discuss the possibility of observing ALPs at this collider as well as an extension to a mixed model of ALPs and dark photon (dark axion portal), that introduces the new couplings not as a product of the individual couplings and therefore offers a rich phenomenology.

Speaker: Marten Berger (University of Hamburg)

15:00 Probing BSM neutral gauge boson in high and low energy experiments

Over a period of time neutral BSM gauge boson is becoming important in the high energy as well as low energy experiments. In this talk we would like to present my recent works where we studied $Z^\prime$, a neutral chiral gauge boson under a general $U(1)$ extension of the Standard Model. In this scenario, there are three generations of right handed neutrinos are introduced which can generate tiny neutrino mass after the breaking of general $U(1)$ gauge group. Studying a variety of low and high energy scattering and beam-dump experiments we will show the current parameter space of the general U(1) coupling as a function of the $Z^\prime$ mass for different U(1) charges.

Speaker: Arindam Das

14:00 → 15:30 Software, Reconstruction, Computing: 1

14:00 Streamlined jet tagging network assisted by jet prong structure

Attention-based transformer models have become increasingly prevalent in collider analysis, offering enhanced performance for tasks such as jet tagging. However, they are computationally intensive and require substantial data for training. In this paper, we introduce a new jet classification network using an MLP mixer, where two subsequent MLP operations serve to transform particle and feature tokens over the jet constituents. The transformed particles are combined with subjet information using multi-head cross-attention so that the network is invariant under the permutation of the jet constituents. The network structure is closely related to the multiscale nature of HEP events.
The proposed network demonstrates comparable classification performance to state-of-the-art models while boosting computational efficiency drastically. The network structure can be applied to the various collider processes.

Speaker: Dr Ahmed Hammad (KEK)

14:20 Jet origin identification for electron positron Higgs factory

To enhance the scientific discovery power of high-energy collider experiments, we propose and realize the concept of jet origin identification that categorizes jets into 5 quark species (b, c, s, u, d), 5 anti-quarks (¯b, ¯c, ¯s, ¯u, ¯ d), and the gluon. Using state-of-the-art algorithms and simulated ν¯νH,H →jj events at 240 GeV center-of-mass energy at the electron-positron Higgs factory, the jet origin
identification simultaneously reaches jet flavor tagging efficiencies ranging from 67% to 92% for bottom, charm, and strange quarks, and jet charge flip rates of 7% to 24% for all quark species.
We apply the jet origin identification to Higgs rare and exotic decay measurements at the nominal luminosity of the Circular Electron Positron Collider (CEPC), and conclude that the upper limits on the branching ratios of H → s¯s, u¯u, d ¯ d, and H → sb, db, uc, ds can be determined to 2×10−4 to 1×10−3 at 95% confidence level.
We also discussed its application on EW and Flavor Physics measurements at future electron-positron Higgs factory.

Speaker: Manqi RUAN (IHEP-LLR/CERN)

14:40 Application of Particle Transformer to quark flavor tagging in the ILC project

International Linear Collider (ILC) is a next-generation e+e- linear collider to explore Beyond-Standard-Models by precise measurements of Higgs bosons. Jet flavor tagging plays a vital role in the ILC project by identification of H->bb,cc,gg,ss to measure Higgs coupling constants and of HH->bbbb and bbWW which are the main channels to measure the Higgs self-coupling constant.
Jet Flavor Tagging relies on a large amount of jet information such as particle momenta, energies, and impact parameters, obtained from trajectories of particles within a jet. Since jet flavor tagging is a classification task based on massive amounts of information, machine learning techniques have been utilized for faster and more efficient analysis for the last several decades.
In recent years, a novel machine learning architecture from natural language processing called Transformer has been developed, and it has been showing state-of-the-art performances in multiple fields. Particle Transformer (ParT) is a software that applies the Transformer architecture to jet analysis, including jet flavor tagging. In this study, we apply ParT to ILD full simulation data to improve the efficiency of jet flavor tagging.
Our research focused on evaluating the performance of ParT compared to the previously used flavor tagging software, LCFIPlus, and optimizing network architectures and input parameters. Specifically, we verified performance stability through multiple training runs, assessed the performance when independently embedding charged particles and neutral particles, and evaluated the dependence on data size and number of learnable parameters. We will also report on the status of performance study of strange tagging using ParT with ILD full simulation, which can be applied on analysis of Higgs-strange coupling.

Speaker: Risako Tagami (University of Tokyo (JP))

14:00 → 15:30 Top, QCD, Flavor, Precision Modelling: 2

14:00 Fragmentation functions at future lepton colliders

Fragmentation functions (FFs) are essential non-perturbative inputs for precision calculations of hadron production cross sections in high energy scattering from first principle of QCD. They are usually extracted from global analysis on world data from single inclusive hadron production at lepton colliders, semi-inclusive DIS and pp collisions, e.g., as in recent NPC23 analysis. Future lepton colliders operated at several center of mass energies will provide high-quality hadron multiplicity data from Z boson to W boson pair as well as Higgs boson production, and ensure an accurate and precise determination of FFs based solely on data from lepton colliders. Projection for several scenarios of future leptons colliders are considered and compared to FFs from most recent global determination.

Speaker: Prof. Jun Gao (Shanghai JiaoTong University)

14:20 Prospects for constraining light-quark electroweak couplings at Higgs factories

Electroweak Precision Measurements are stringent tests of the Standard Model and sensitive probes to New Physics. Accurate studies of the Z-boson couplings to the first-generation quarks could reveal potential discrepancies between the fundamental theory and experimental data. Future e+e- colliders running at the Z pole and around the ZH threshold would be an excellent tool to perform such a measurement, unlike the LHC where hadronic Z decays are only available in boosted topologies. The measurement is based on comparison of radiative and non-radiative hadronic decays. Due to the difference in quark charge, the relative contribution of the events with final-state radiation (FSR) directly reflects the ratio of decays involving up- and down-type quarks. Such an analysis requires proper modeling and statistical discrimination between photons coming from different sources, including initial-state radiation (ISR), FSR, parton showers and hadronisation. In our contribution, we show how to extract the values of the Z couplings to light quarks and present the estimated uncertainties of the measurement.

Speaker: Krzysztof Mekala

14:40 Reimagining Linear Collider Luminosity Measurement

Our recent work has shown that a novel, much higher granularity
forward calorimetry concept can enable much more detailed and precise
reconstruction than the baseline designs based on LEP luminometers, together
with the capability of electron/positron/photon separation.

This new calorimeter concept is designed primarily to maximize the acceptance
for ${e}^{+}e^{-} \to \gamma \gamma$ as an alternative luminosity process, where it serves
to define the inner edge of the acceptance (there is no outer edge - as the
complete detector is used in the measurement), while continuing to provide
the standard luminosity measurement from small angle Bhabhas. It will also
serve as a general forward electromagnetic calorimeter helping ensure hermeticity
and detecting individual electrons, positrons and photons.

In this contribution we will highlight the Bhabha rejection capability in the
context of the ${e}^{+}e^{-} \to \gamma \gamma$ luminosity measurement and investigate the
utility of a Bhabha ``mini-tracker'' consisting of a few planes of
upstream thin silicon detectors. This will further refine the $e^{+}$/$e^{-}$ polar angle
measurement, improve Bhabha rejection (for $\gamma \gamma$), and,
last-but-not-least, help mitigate the beam-induced electromagnetic deflection
that biases the Bhabha acceptance by providing high precision longitudinal
vertex information in Bhabha events than can be used in diagnosing this
beam/final-state $e^{+}$/$e^{-}$ effect.

Speaker: Graham Wilson

15:00 Third family quark mass hierarchy and FCNC in the universal seesaw model

We study the quark sector of the universal seesaw model with $SU(2)_L × SU(2)_R × U(1)_{Y'}$ gauge symmetry in the massless limit of the two lightest quark families. This model aims to explain the mass hierarchy of the third family quark by introducing a vector-like quark partner for each quark. In addition to the Standard Model Higgs doublet, we also introduce one right-handed Higgs doublet. In this presentation, we show the $Z, Z’, h, H$ FCNC for the third family quark ($t,b$) and the heavy partner ($t’,b’$).

Speaker: Albertus Panuluh (Hiroshima University)

15:15 → 15:45 coffee

15:45 → 17:45 Industry: Sustainability

15:45 Efforts toward a Green ILC in Japan

We are working on various activities to achieve sustainability of the ILC during its total life cycle. Japanese companies are making efforts to promote decarbonization during the production of concrete, steel frame and rebar, which account for a large portion of CO2 emissions during construction. During operation, most of the CO2 emissions come from the electricity used by the ILC, and efforts are being made to make the electricity in the area where the ILC candidate site is located sustainable. Efforts are also underway to increase CO2 absorption in forests and coastal areas, and to increase the long-term fixation of CO2 by incorporating more wood structures in local housing and large public buildings including ILC-related facilities. This report discusses these efforts.

Speaker: Masakazu Yoshioka (KEK)

16:00 CEPC Green Accelerator Technology Development

The Circular Electron Positron Collider (CEPC) is a proposed high-energy physics facility designed to advance the frontiers of scientific research while maintaining a strong commitment to environmental sustainability. This paper explores the global trend towards greener accelerators and outlines the specific initiatives undertaken by the Institute of High Energy Physics (IHEP). International efforts have focused on enhancing integrated management capabilities, improving energy utilization efficiency of various measurements. IHEP's green initiatives for particle accelerators are noteworthy. These include the large-scale utilization of solar energy, the pioneering adoption of permanent dipole magnets in China for the High Energy Photon Source (HEPS) facility, the development of high-efficiency klystrons, improvements in the Q value of superconducting high-frequency cavities and superconducting magnets, recycling of liquid helium, optimization of large cryogenic systems, and the practical application of waste heat resources. However, the transition to greener accelerators faces some challenges and difficulties. These range from the need for new theories and schemes to technological limitations and economic considerations, etc. Despite these difficulties, the outlook is promising, with the potential for significant reductions in energy consumption, emissions, and waste generation. In summary, through the green initiatives and contributions to the global green accelerator movement of CEPC, it paves the way for a more environmentally sustainable future in particle accelerator facilities.

Speaker: Rui Ge (IHEP，CAS)

16:15 A Sustainability Strategy for the Cool Copper Collider

In this talk, we will discuss the studies presented in PRX ENERGY 2, 047001, where the carbon impact of the Cool Copper Collider ($C^3$), a proposed electron-positron linear collider operated at 250 and 550 GeV center-of-mass energy, is evaluated. We introduce several strategies to reduce the power needs for $C^3$ without modifications in the ultimate physics reach. We also propose a metric to compare the carbon costs of Higgs factories, balancing physics reach, energy needs, and carbon footprint for both construction and operation, and compare $C^3$ with other Higgs factory proposals – ILC, CLIC, FCC-ee and CEPC – within this framework. We conclude that the compact 8 km footprint and the possibility for cut-and-cover construction make $C^3$ a compelling option for a sustainable Higgs factory. More broadly, the developed methodology serves as a starting point for evaluating and minimizing the environmental impact of future colliders without compromising their physics potential.

Speaker: Brendon Bullard (SLAC National Accelerator Laboratory)

16:30 Sustainability Efforts for Present and Future Accelerator Facilities

Increasing awareness and action on sustainability efforts for current and future accelerators has led to notable progress in recent years. Higher priority has to be given to environmental sustainability including energy consumption, natural resource use and the environmental impact of effluents. Typically, increased performance - higher beam energies and intensities - of proposed new facilities have come with increased electric power consumption. In this presentation on behalf of the ICFA Sustainability panel, we will discuss the most important areas of development for the sustainability of accelerator-based research infrastructures in three categories - technologies, concepts and general aspects.

Speaker: Emilio Nanni (SLAC National Accelerator Laboratory)

16:45 Lifecycle Inventory input to an LCA for ILC and CLIC

As input for the planned Lifecycle Assessment (LCA) of the ILC and CLIC projects, Lifecycle Inventory (LCI) data has been collected. The most important components in terms of environmental impact, in particular greenhouse gas (GHG) emissions, are estimated to be the accelerating structures (cryo modules for ILC, two beam modules for CLIC), magnets, RF supply system, cryogenics, vacuum system, and the detectors. We present our approach and preliminary results to the quantification of energy and material inputs during the lifecycle stages of the accelerator.

Speaker: Steffen Doebert (CERN)

17:15 Need of the hour: Carbon Utilized Concrete (CUCO)

Concrete, the quintessential construction material composed of cement, water, sand, and aggregates, is indispensable for infrastructure and societal advancement. As the threat of climate change looms, the construction industry is striving to reduce the carbon emissions from concrete production. This study offers an in-depth analysis of practical applications and introduces advanced technologies designed for mass production of eco-friendly, low-carbon concrete.
The research outlines three innovative strategies to reduce concrete's carbon footprint. The first substitutes traditional cement with industrial by-products like blast furnace slag, fly ash and recycled cement lowering associated carbon emission. The second employs cutting-edge admixtures that promote CO2 absorption during curing, enabling CO2 mineralization within the concrete matrix. The carbonation curing not only sequesters CO2 but may also improve concrete's material properties. The third strategy integrates waste material processed using mineral carbonation technique and applied as sustainable aggregate alternatives.
The feasibility of above strategies needs to be supported by the development of green technologies and specialized machinery. After years of comprehensive research regarding carbonation curing of concrete, the carbonation chamber, a sophisticated device that expedites the carbonation of concrete has been developed. It provides a controlled CO2 rich environment for efficiently mineralizing CO2 from exhaust gases within concrete at an enhanced rate, effectively transforming concrete into a carbon sink. Another significant advancement is the creation of large-scale carbonation reactors that collect calcium rich highly alkaline industrial effluents, followed by processing and mineralizing CO2 into stable calcium carbonate. Furthermore, in-depth research is being conducted on development of methods so that by-product can be incorporated into concrete without compromising its integrity and properties.

Speaker: Kumar Avadh (Kajima Corporation)

17:25 Challenges and breakthroughs in recent RF Solid State PA design by Radial Combiner design with Initiatives for SDGs

R&K, an independent company, has achieved production of 2.3 million 1.9GHz microwave power amplifiers for mobile-comm’s-base-stations and then also supplies wideband power amplifiers for automobile EMC testing for domestic automobile industries. Then 16 years ago, we started new design and producing some hundreds kW RF SSA for accelerator applications instead of Klystron / tube alternatives.
The measure characteristics of this amplifier is possible to design a band in a very wide frequency range available from few MHz to 14 GHz, and there is also max-power-changing capability in few kW to few MW design available even after system completed. Recently, SSA has gained significant advantages over vacuum tubes in terms of size, low power consumption, high efficiency, low cost, and adaptive power design. In addition to these, we have found that SSA has very low phase noise and low envelope noise that cannot be achieved with vacuum tubes.
All these points suggest a strong trend toward solid-state amplifiers and a move away from vacuum tube systems, even for power amplifiers used in particle accelerators. There is no doubt that all these improved performances will eventually lead to a strong trend towards his SDGs.

Speaker: Mr Riichiro Kobana (R&K Company Limited)

17:35 Commercialization and fundamental research of waste heat recovery technology using adsorption heat storage materials

○Goh Mitoya, Yuichi Kouno (HKK), Masaya Suzuki, Kazuko Manpuku (AIST), Takashi Kokubo, Masayuki Tanino, Gen Sato, Shinichi Muraoka (Takasago Thermal Engineering Co., Ltd.), Fukumi Takahashi, Yasunori Anetai (WING Co., Ltd.), Hisashi Odaira, Kazuya Kikuchi (Iwate Prefectural Office), Ichiro Hirosawa(SAGA-LS), Masakazu Yoshioka, Shinya Narita, Noriyuki Yoshimoto, Satomi Fujisaki, Yoichi Takeda (Iwate University)

Abstracts:
Based on the Green ILC concept, an R & D program is underway to recover and utilize thermal energy emitted from the cooling water of ILC facilities.
Iwate Prefecture, where the ILC Kitakami candidate site is located, is 80% mountainous, which is not suitable for online transportation of thermal energy.
In order to effectively utilize the thermal energy emitted from the ILC facilities, a thermal energy circulation model suitable for such regional characteristics is required.
We are aiming to commercialize an off-line waste heat circulation model that utilizes an innovative adsorptive thermal storage material, ”HASClay", which can utilize low-grade waste heat of 50-100℃.
So far, we have developed a portable container that can hold approximately 10 kg of dry HASClay and have evaluated its heat storage and emission performance.
On the other hand, one of the issues for practical use is to elucidate the mechanism of water vapor adsorption/desorption on the microstructure of "HASClay".
Here, we discuss two issues: (1) a demonstration test for commercialization of a thermal energy circulation model and (2) basic research to understand the structure and adsorption/desorption mechanism of "HASClay" using synchrotron radiation.

Speaker: Yuichi Kouno

18:00 → 20:00 Plenary: Sachio Komamiya memorial

Conveners: Masaya Ishino (University of Tokyo (JP)), Taikan Suehara (ICEPP, The University of Tokyo)

18:00 Opening remarks

Speaker: Masaya Ishino (University of Tokyo (JP))

18:10 Rolf Heuer

Speaker: Rolf Heuer (CERN)

18:20 Michael Peskin

Speaker: Michael Peskin

18:30 Kiyotomo Kawagoe

Speaker: Kiyotomo Kawagoe (Kyushu University)

18:40 Shion Chen

Speaker: Shion Chen (Kyoto University (JP))

18:50 Andy White

Speakers: Andrew White (University of Texas at Arlington (US)), Andy White

19:00 Remarks from Participants

19:25 Closing

Speaker: Prof. Toshinori Mori (University of Tokyo (JP))

Wednesday, 10 July

09:00 → 10:30 BSM, Global Interpretations: 3

09:00 Recent updates of BSM searches at CMS and future prospects at HL-LHC

This talk covers recent highlights of BSM searches from the CMS experiment and future prospects at HL-LHC.

Speaker: Jeongeun Lee (Seoul National University (KR))

09:25 Searches for Long-Lived Particles at the Future FCC-ee

The electron-positron stage of the Future Circular Collider, FCC-ee, is a frontier factory for Higgs, top, electroweak, and flavour physics. It is designed to operate in a 100 km circular tunnel built at CERN, and will serve as the first step towards ≥ 100 TeV proton-proton collisions. In addition to an essential and unique Higgs program, it offers powerful opportunities to discover direct or indirect evidence of physics beyond the Standard Model. Direct searches for long-lived particles at FCC-ee could be particularly fertile in the high-luminosity Z run and at other collision energies. Several physics cases producing long-lived signatures at FCC-ee are highlighted in this contribution: heavy neutral leptons (HNLs), axion-like particles (ALPs), and exotic decays of the Higgs boson.

Speaker: Nicola De Filippis (Politecnico e INFN, Bari (IT))

09:50 Long-lived particle searches with the ILD experiment

Future e$^+$e$^-$ colliders, with their clean environment and triggerless operation, offer a unique opportunity to search for long-lived particles (LLPs). Considered in this contribution are prospects for LLP searches with the International Large Detector (ILD) providing almost continuous tracking in Time Projection Chamber (TPC) as the core of its tracking systems. The ILD has been developed as a detector concept for the ILC, but is also applicable to other Higgs Factory options.

The considered signature for neutral LLP production is a highly displaced decay vertex, which we search for in the TPC. Based on the full detector simulation, we study decays of both light and heavy LLPs. For the heavy, $\mathcal{O}$(100 GeV) LLPs, the most challenging scenarios are those with a small mass splitting between LLP and the dark matter candidate, resulting in only a very soft displaced track pair in the final state, not pointing to the interaction point. As the opposite extreme scenario we consider the production of light, $\mathcal{O}$(1 GeV) pseudo-scalar LLP, which decays to two highly boosted and almost colinear displaced tracks. Backgrounds both from soft beam-induced processes and hard physical events are taken into account. Different tracking system design options and their impact on the LLP reconstruction are discussed.

Assuming a single displaced vertex signature, the limits on signal production cross-section are presented for a wide range of LLP lifetimes and a set of masses or mass splittings. These limits are to a large extent model-independent, reflecting kinematic properties of the considered signature. They can be used to set limits on particular models, also for more complex signatures involving displaced vertices.

Speaker: Jan Klamka (University of Warsaw)

10:10 Unconventional Searches of Exotic particles at Future Linear Colliders

Current collider experiments, such as LHC have been studying the production of the BSM particles and their decay to the Standard Model particles. These searches have placed strong constraints on different BSM models as well as on the mass of BSM particles. The situation demands to look for alternative scenarios. BSM theories such as the Pati Salam Model, Composite Higgs, and others suggest that the interaction among different BSM particles exists such that the exotic particle of one type decays to the exotic particle of type two first then to the SM particles. This in turn reveals exciting new signatures. Now, due to the long decay chain, a large number of particles are present at the final state. If the final state is accompanied by a large number of jets, then linear colliders offer a much cleaner environment to study them. Moreover, photon-photon fusion also provides a large cross-section. In this talk, I will discuss some of these alternative searches of exotic fermion and scalars at future colliders such as the International Linear Collider and photon photon collider.

Speaker: Dr Nilanjana Kumar (CCSP, SGT University, India)

09:00 → 10:30 Beam Dynamics: 1

09:00 Multi-bunch beam dynamics studies in the C3 main linac

The Cool Copper Collider (C3) is a novel electron-positron linear collider concept that utilizes a cryogenically-cooled copper accelerator technology. It is designed to accelerate 133 bunches of electrons/positrons from 10 GeV to 125 GeV while preserving the beam quality. In order to achieve the target beam’s luminosity, careful studies of the long-range higher order modes (HOM) wakefield effects must be taken into account for the design of the accelerating structure. Here we present the analysis of the beam dynamics studies for the long range HOM wakefields. We will show the accelerator operating parameters and important frequency bands that deteriorate the beam. After that, we present detuning and damping results which are then used to guide the design of the accelerating structure.

Speaker: Wei-Hou Tan (SLAC)

09:20 Luminosity Studies for the Cool Copper Collider

Achieving high instantaneous luminosity while managing the beam-induced background (BIB) is critical for the successful operation of any future electron-positron ($e^{+}e^{-}$) collider. In this talk, we will present the first extensive luminosity studies for a proposed linear $e^{+}e^{-}$ collider, the Cool Copper Collider (C$^3$), as discussed in arXiv:2403.07093. We begin with a theoretical overview of luminosity at $e^{+}e^{-}$ colliders and its interplay with Beamstrahlung – the leading source of BIB – and we motivate the importance of simulations for the accurate evaluation of the effect of beam-beam interactions on the attainable luminosity. Through simulations in Guinea-Pig, we then evaluate the impact of key beam parameters, such as emittance, bunch length, beta function and waist shift, on the luminosity of C$^3$, and tune these parameters with the objective of optimizing the luminosity, without a commensurate increase in the accompanying BIB. We then propose a new beam parameter set for C$^3$ which achieves a ~40% luminosity increase while maintaining BIB levels at similar levels. Additional luminosity-enhancing scenarios through modifications in the time-structure of the beam are presented, and their sustainability implications are discussed. Finally, using a common simulation framework, we perform a comparative analysis of the luminosity and BIB characteristics of C$^3$ with those for ILC and CLIC. Our results indicate that C$^3$ achieves competitive luminosities with a narrower luminosity spectrum than CLIC and lower background rates than ILC, placing C$^3$ as an attractive option for realizing a compact, high-performance Higgs factory. We close our talk by showing how the developed luminosity optimization methodology can be extended to other collider proposals and by presenting preliminary results towards an automatized luminosity optimization scheme.

Speaker: Dimitris Ntounis (SLAC National Accelerator Laboratory (US))

09:40 ILC beamline update

The present ILC beamline will be presented.

Speaker: Kiyoshi Kubo (KEK)

10:00 Machine Learning studies at KEK

Machine Learning studies at KEK will be presented.

Speaker: Dr Masakazu Kurata (KEK)

09:00 → 10:30 Calorimetry, Muon detectors: 2

09:00 Status of high granular scintillator calorimeter for future electron positron colliders

Several future Higgs factories are planned for the precision Higgs physics to search for the new physics. The highly granular calorimeters play a crucial role on the precision Higgs measurement. The highly granular Sc-ECAL is based on a scintillator strip readout by a SiPM to realize the 5 mm × 5 mm cell size by aligning the strips orthogonally in x-y configuration. In order to demonstrate the performance of the Sc-ECAL and the scalability to the full-scale detector, the technological prototype has been developed with full 32 layers. In 2022 and 2023, the combined beam test of the Sc-ECAL and the CEPC-AHCAL, which is the scintillator based HCAL designed for the Circular Electron Positron Collider, is conducted at CERN SPS and PS beam lines to demonstrate the full calorimeter performance and the per-channel calibrations and performance demonstration are successfully done. This presentation describes the status the Sc-ECAL analysis of the combined beam test.

Speaker: Tatsuki Murata

09:30 Test beam experiment of the large prototype of high granularity scintillator calorimeter for future electron-positron colliders -performance evaluation -

Future electron-positron colliders, including the International Linear Collider (ILC) and the Circular Electron Positron Collider (CEPC), are currently proposed for the precise measurement of the Higgs boson. These projects require high-resolution scintillator calorimeters to achieve fine granularity. Our research focuses on the development of potential calorimeter options, namely the Scintillator Electromagnetic Calorimeter (Sc-ECAL) and the Analog Hadron Calorimeter (AHCAL). These are sampling calorimeters that use plastic scintillator cells as detection layers, with absorber layers that generate showers and detection layers that capture particles from these showers alternately arranged. To demonstrate the capabilities of these calorimeters, a prototype consisting of 32 layers of ECAL and 40 layers of HCAL, reflecting the actual device design, was constructed. Between April and June 2023, a beam test using this integrated prototype was conducted at CERN. The tests involved muons (10, 100, 120 GeV), electrons (0.5–250 GeV), and pions (1–350 GeV) to evaluate the energy response and resolution of ScECAL and AHCAL for electrons and pions. This presentation will outline each detector and the beam test, and report the analysis results concerning the performance of the detectors during the beam tests.

Speaker: Taisei Takatsu (ICEPP)

10:00 Test-beam measurements of instrumented sensor planes for a higly compact and granular electromagnetic calorimeter

The LUXE experiment is designed to explore the strong-field QED regime in interactions of high-energy electrons from the European XFEL in a powerful laser field. One of the crucial aims of this experiment is to measure the production of electron-positron pairs as a function of the laser field strength where non-perturbative effects are expected to kick in above the Schwinger limit.

For the measurements of positron energy and multiplicity spectra, a tracker and an electromagnetic calorimeter are foreseen. Since the expected number of positrons varies over five-orders of magnitude, and has to be measured over a widely spread low energy background, the calorimeter must be compact and finely segmented. The concept of a sandwich calorimeter made of tungsten absorber plates interspersed with thin sensor planes is developed. The sensor planes comprise a silicon pad sensor, flexible Kapton printed circuit planes for bias voltage supply and signal transport to the sensor edge, all embedded in a carbon fibre support. The thickness of a sensor plane is less than 1 mm. A dedicated readout is developed comprising front-end ASICs in 130 nm technology and FPGAs to orchstrate the ASICs and perform data pre-processing. As an alternative, GaAs are considered with integrated readout strips on the sensor. Prototypes of both sensor planes are studied in an electron beam of 5 GeV. Results will be presented on the homogeneity of the response, edge effects and cross talk between channels.

Speaker: Yan Benhammou (Tel Aviv University (IL))

09:00 → 10:30 Higgs, Electroweak: 2

09:00 Electroweak measurements at the LHC and HL-LHC (Invited)

Invited talk on the electroweak measurements at the LHC and HL-LHC.

Speaker: Anne-Marie Magnan (Imperial College (GB))

09:30 Searching for new physics in WW and single-W events

Pair- and single-production of W bosons provide many opportunities to look for new physics via precision measurements, for instance via scrutinizing the involved triple-gauge vertices or by measuring CKM matrix elements in an environment very complementary to B hadron decays. This contribution presents the ongoing work based on full simulation of the ILD detector concept, exploiting the O(10^8) W bosons produced during the 250 GeV stage of the ILC.

Speaker: Jenny List (Deutsches Elektronen-Synchrotron (DE))

09:50 Higher-order initial state radiation in e+e- annihilation

Radiative corrections due to initial state radiation in electron-positron
annihilation are calculated within the QED structure function approach. NLO QED parton distribution functions are derived analytically. Results are shown in the next-to-leading logarithmic approximation up to $\mathcal{O}(\alpha^4 L^3)$ order, where $L=\ln(s/m_e^2)$ is the large logarithm. Several mistakes in previous calculations are corrected. The results are relevant for future high-precision experiments at $e^+e^-$ colliders.

Speaker: Andrej Arbuzov (Joint Institute for Nuclear Research)

10:10 New renormalization scheme in extended Higgs sectors for Higgs precision measurements

We propose a new renormalization scheme in extended Higgs sectors for the coming new era of the Higgs precise measurements at future lepton colliders. In this new scheme, we use a precisely measured value of the discovered Higgs boson coupling, e.g., hZZ, as an input of the renormalization condition. We demonstrate how the other Higgs boson couplings (e.g., hWW) can be predicted. in this new renormalization scheme in the 2 Higgs doublet model as a simple but important example.

Speaker: Kei Yagyu (Osaka University)

09:00 → 10:30 Normal conducting RF: 2

09:00 Capture Cavities for the CW Polarized Positron Source Ce+BAF

The initial design of the capture cavities for the continuous wave (CW) polarized positron beams at Jefferson Lab (Ce+BAF) is presented. A chain of standing wave multi-cell copper cavities inside a solenoid tunnel are selected to bunch/capture positrons. The cavity design strategy is presented to accommodate constrains from the large phase distribution of the incident beams, RF power, radiation and RF heating, beam loading, etc. to improve the capture efficiency. A matrix of design parameters' range are given for future system optimization when the the capture cavities are considered together with other sub-systems and beam dynamics. The contents will also be useful for other CW cavity design for beams with large phase space distribution.

Speaker: Shaoheng Wang (Jefferson Lab)

09:20 Status and Plans for the C3 Quarter Cryomodule

To achieve target performance of the C3 accelerator, many elements will need to be manufactured, assembled, and aligned in use to very tight tolerances. Testing of accelerating structure manufacturing, alignment, mounting, and liquid nitrogen cooling will be performed at SLAC using an accelerator length of approximately 2 meters. This talk will review progress and plans toward commissioning a Quarter Cryo-Module “QCM” test system including the design of a 1 meter length of accelerating structure and the support and alignment system required for test. This system review will include details of the vacuum insulated cryostat sized to allow testing 2 sections of 1m long accelerating structure with quad and BPM supported on a frame representative of a system that could be used in the C3 target cryo-module containing 8 meters of accelerating structure. It is intended that the QCM system will be used to evaluate a series of accelerating structures, supports, and measurements techniques. Some of the initial plans will be reviewed in this talk.

Speaker: Mr Haase Andy (SLAC National Accelerator Laboratory / Stanford University)

09:40 High Gradient Testing of a Meter-Scale Distributed-Coupling C3 Accelerating Structures

In this paper we report on the design, fabrication, tuning and high-power RF testing of the fundamental accelerating structure for the Cool Copper Collider (CCC). The results presented here cover the temperature range from room temperature to liquid nitrogen boil off: 20oC - 77 K

At room temperature, RT, with a N2 gas purge of 1 atmosphere, the CCC structure was tuned to a resonance frequency of < fo> = 5.693 420 GHz, at 77K the structure tuned frequency is reported as < fo> = 5.712 057 667 GHz. The repeatability of the CCC structure to undergo both vacuum pump down and thermal cycles from RT to LN2 will be presented.

For the high-power RF testing the CCC structure was immersed in liquid nitrogen at the Radiabeam C-Band test facility. High Power RF breakdown data will be present along with our future experimental plans.

Speaker: Dennis Palmer (SLAC National Accelerator Laboratory / Stanford University)

10:00 Cold Copper High Gradient Single-Cell Structure Tests

We will present results from high gradient structure testing of C-band single-cell copper (Cu) and copper silver (CuAg) accelerating structures at 77 K. C-band accelerators have been of particular interest in recent years due to their ability to provide high gradients and transport high charge beams for applications ranging from colliders to medical technologies. These technologies are made possible by new advances in high gradient technologies that can suppress the breakdown rates by using distributed coupling, cryogenic cooling, and copper alloys. Previous work has shown each of these separately to significantly improve the maximum achievable gradient. In this work, for the first time, we combine all three methods in an ultra-high gradient structure and benchmark the difference between Cu and CuAg. These structures are tested at 77K simultaneously through a hybrid manifold while breakdown statistics were collected. In addition, we will show that at gradients exceeding 200 MeV/m the presence of significant beam loading caused a suppression in the quality factor as a function of time.

Speaker: Emilio Nanni (SLAC National Accelerator Laboratory)

09:00 → 10:30 Sources: 2

09:00 The Compact Positron Source

We present designs and plans for a university-scale positron source that can deliver low-emittance beams for experiments [1]. The source is based on a Penning-Malmberg trap. We discuss positron generation and extraction, with specific focus on bunch manipulation at the exit of the trap. We describe some applications of positron beams from the trap.

[1] Compact source of positron beams with small thermal emittance. R Hessami and S Gessner, Phys. Rev. Accel. Beams 26, 123402 (2023)

Speaker: Spencer Gessner (SLAC)

09:20 CFD simulations of high power positron converter targets

High power converter positron targets can be designed and assessed thermally with computational fluid dynamics (CFD). I will present the CFD assessments of a high power liquid Xenon (LXe) target and a rotating tungsten target with the ILC time structure for the beam.

Speaker: Silviu Covrig Dusa (Jefferson Lab)

09:40 Spin-polarized electron sources for future linear colliders

Spin-polarized electron photoelectron sources are a critical component of multiple future collider designs. The present state-of-the-art polarized electron photocathode material, negative electron affinity gallium arsenide, has remarkable performance: it possesses high quantum efficiency and can emit beams with a spin polarization exceeding 90% under the right conditions. However, its extreme vacuum sensitivity limits its application to guns with extreme high vacuum quality; this has the effect of constraining the peak source brightness. This vacuum sensitivity also limits the average current of the source. Both of these factors can constrain collider luminosity. In this presentation, I will describe alternatives to GaAs photocathodes such as GaN and alkali antimonide photocathodes, which have been demonstrated to emit spin-polarized electrons and have been shown to be much more robust to vacuum poisoning and high average current delivery. After describing these materials, I will discuss the prospects and potential performance of their use in high-field RF electron sources with high peak brightness.

Speaker: Jared Maxson (Cornell University)

10:00 Beam loading simulations of the CLIC positron Source

The presentation will report on recent CLIC positron source activities.
The focus will be on flux concentrator developments and beam loading calculations of the capture LINAC.

Speaker: Nafiseh Mesbah (IPM)

09:00 → 10:30 Superconducting RF: 3

Convener: Sergey Belomestnykh

09:00 Traveling Wave Demonstration in SRF Cavity With a Feedback Waveguide

Conventional SRF cavities are used in standing wave regime and are limited by surface fields to ~50 MV/m. In order to overcome this limit, Superconducting Traveling Wave (SCTW) cavity was proposed as it allows to achieve ~1.5 times higher accelerating gradient operating at lower phase advance per cell, thus improving transit time factor. However, power recirculation through a feedback waveguide is required to maintain cavity efficiency. Funded by the U.S. Department of Energy's SBIR program, Euclid Techalbs, in collaboration with Fermilab, demonstrated in the past the surface processing capability of a single-cell prototype with a feedback waveguide. Subsequently, a 3-cell prototype was designed and fabricated to demonstrate a traveling wave regime in SRF cavity with a feedback waveguide at cryogenic temperatures and the highest gradients. Here we present our recent results of traveling wave demonstration in the 3-cell prototype, tested in 2K liquid helium at Fermilab.

Speaker: Roman Kostin (Euclid Techlabs)

09:20 Development of a half-meter scale Traveling-Wave (TW) SRF cavity

While a demonstration of TW resonance excitation in the 3-cell structure in 2K liquid helium had been prepared and carried out at Fermilab in collaboration with Euclid Techlabs, the RF design process of 0.5~1 meter scale TW cavity was begun at Fermilab as the next step of TW development towards an accelerator-scale one. Considering the physical dimensions of existing SRF facilities (for fabrication, processing, and cryogenic testing), Fermilab has proposed a half-meter scale TW RF design consisting of a 7-cell structure and a power feedback waveguide (WG) loop. The WG loop design includes the new RF configurations for TW resonance control during a high-power operation. 1-year US-Japan collaboration program focused on EBW optimization for the TW shape iris joint within the narrow gap was awarded and the efforts had been made by KEK, Jlab, and Fermilab. 1-year LDRD program of Fermilab is awarded recently to fabricate a low-cost mockup of the WG loop with new RF configurations and validate them. Here we will present a preliminary 7-cell TW RF design and report the progress and challenges through the awarded programs.

Speaker: Dr Fumio FURUTA (Fermilab)

09:40 High Power RF Testing of REBCO Samples

SRF materials such as niobium have been extremely useful for accelerator technology but require low temperature operation ~4K. The development of high temperature superconductors (HTS) is promising due to their operating temperatures being closer to that of liquid nitrogen ~77K. This work hopes to determine the high-power RF performance of such materials at X-band (11.424 GHz). We have tested two kinds of REBCO coatings, film deposited, and tapes on a copper substrate. Testing was done in a hemispherical TE mode cavity due to its ability to maximize the magnetic field on the sample and minimize electric field. We will report on conductivity vs temperature measurements at low and high power, as well as preliminary tests of a TM01 cavity which could utilize REBCO tapes. We have observed quenching within these REBCO samples and explain the evidence which implies that the quenching is most likely due to reaching the critical current and due to average applied heat load for powers up to 1.6 kW.

Speaker: Ankur Dhar (SLAC National Accelerator Lab)

09:55 ILC Upgrade with Energy Revovery

Several proposals of e+e- colliders with energy recovery
concept have been proposed in the last few years. I shall
discuss about possible upgrade of ILC in the far future
using energy recovery linacs.

Speaker: Kaoru Yokoya

10:10 The fabrication of the 1.3 GHz single-cell cavity utilizing the different grain size niobium materials

As the part of research into the manufacturing methods for SRF cavities used in ILC(International Linear Collider), two 1.3 GHz single-cell cavities have been fabricated by utilizing fine and medium grain size niobium materials, respectively, with the same manufacturing equipment. The fine grain size niobium material typically exhibits a grain size level equivalent to ASTM 5-6, whereas the medium grain size corresponds to ASTM 0-3 levels. The forming of the half cell shapes has been conducted using the same deep drawing die and press machine. The machining for cavity part fabrication and the welding for assembly have been carried out using identical jigs and equipment. We present the fabrication processes and the test results for cavities in detail.

Speaker: Dr Junho Han (Kiswire Advanced Technology Co., Ltd.)

09:00 → 10:30 Vertex, Tracking, Timing detectors: 2

09:00 Status of the drift chamber project for the IDEA detector proposal for FCC-ee

The future circular electron-positron collider FCCee is receiving much attention in the context of the FCC Feasibility Study currently in progress in preparation for the next EU strategy update. The most recent status of the R&D of the drift chamber project for the IDEA detector concept is presented. We discuss the physics requirements, the technical solutions chosen to address them, the performance of the cluster counting technique to improve the particle identification capability of the detector by using testbeam data, and the further steps on the path of the construction of a full-lenght prototype.

Speaker: Nicola De Filippis (Politecnico e INFN, Bari (IT))

09:20 Drift chamber with cluster counting techniques for CEPC

The Circular Electron Positron Collider (CEPC) is a large-scale collider facility with a circumference of 100 km. It is designed to study rich physics programs, including investigations into Higgs properties, electroweak physics and flavor physics. A good identification of charged hadrons is essential for the flavor physics and benefits the determination of jet flavor and jet charge. To achieve these physics goals, a drift chamber is proposed for excellent particle identification (PID) performance with the cluster counting technique. Cluster counting measures the number of primary ionizations (dN/dx) along the particle trajectory in a gaseous detector, rather than relying on energy loss (dE/dx). This approach represents a promising breakthrough in PID. The Poissonian nature of dN/dx provides a statistically significant way to measure ionization, potentially yielding a resolution two times better than dE/dx.
A detailed PID study of the drift chamber will be presented. Simulation studies, including the detector and electronics responses, as well as the machine-learning reconstruction algorithm, are performed to optimize the detector design and performance. The PID results using dN/dx and time-of-flight show that the kaon and pion separation power, with a track length of 1.2 m, can achieve a 3σ significance for momenta less than 20 GeV/c. Mechanical design has been carried out and finite-element-analysis results demonstrate a stable design. Fast readout electronics have been developed, and a detector prototype has been tested with an electron beam. The test results validate the performance of the electronics and the feasibility of the dN/dx method.

Speaker: Dr Guang Zhao (IHEP)

09:40 Tracking Performance Study for Future Circular Collider (FCCee) with CLD Detector

The Future Circular Collider electron-positron (FCCee) feasibility study involves assessing the capabilities and performance of potential detector configurations. This study focuses on the impact of various detector parameters on tracking performance. Specifically, the influence of different geometries, material budgets, and magnetic field strengths on the precision and efficiency of tracking performance within the CLIC-Like Detector is investigated.

Tracking performance is evaluated using full simulations. The effects on track reconstruction efficiency and resolution are assessed by adjusting the detector geometry and material. Additionally, the influence of magnetic field strengths on tracking accuracy is explored.

This study provides valuable insights into optimising the design parameters of the FCCee detector to achieve high tracking performance, contributing essential information for the ongoing FCCee feasibility study and future collider detector development.

Keywords: FCCee feasibility study, CLD, Full simulation, tracking performance, detector geometry

Speaker: Gaelle Sadowski (Centre National de la Recherche Scientifique (FR))

10:00 High Granularity Readout TPC R&D for Tera-Z at the Future e+e- Collider

The future linear and circular electron positron colliders were been proposed as a Higgs and a high luminosity Z factory in last few years. The detector conceptual design of a updated detector consists of a tracking system, which is Time Projection Chamber (TPC) detector as the main track with the high precision (about 100$\mu$m overall drift length at 3T magnetic field) spatial resolution device in the large 3D volume, especially for the case of the machine operating at the high luminosity Z pole (Tera-Z at 2T magnetic field). Aimed to Higgs and the flavor physics requirements, the tracking system required the high precision performance,including the spatial resolution, the momentum resolution and the good particle identification detection (PID).

TPC detection technology also required the longitudinal time resolution of about 100ns and the physics goals require the very good separation power with the cluster counting to be considered. The simulation and PID resolution show TPC technology potential to extend Tera-Z at the future e+e- collider. In this talk, the feasibility and status of high precision TPC as the main track detector for e+e collider will be presented. The simulation results of the pad/pixelated TPC technology for e+e- collider will be given. Compared with the pad readout using the simulation, the high granularity readout TPC option will obtain the better spatial resolution of single electrons, the very high detection efficiency in excellent tracking and good PID performance (less than 3$\sigma$).

Speaker: Dr Huirong Qi (Institute of High Energy Physics, CAS)

10:30 → 11:00 coffee

11:00 → 12:30 BSM, Global Interpretations: 4

11:00 Heavy Neutral Leptons (HNL) at e+e- colliders - theory

In this talk I will review the models motivating searches for heavy neutral leptons at future e+e- colliders by linking their properties to different frameworks for neutrino mass generation and mixing. Several different regimes of prompt decays vs. long-lived HNLs vs. displaced tracks will be discussed together with their experimental signatures.

Speaker: Jürgen Reuter (DESY Hamburg, Germany)

202407_LCWS_HNL_JRR.pdf

11:20 HNL at e+e- colliders

Neutrinos can be a key to solving several cosmological problems, such as the mystery of the baryon-antibaryon asymmetry in the universe or the origin of dark matter. The existence of their heavier partners, the so-called heavy neutral leptons (HNL), is a well-motivated scenario which could also contribute to explaining the mass-generation mechanism for light neutrinos. Future lepton colliders, including e+e- linear machines, will offer the farthest discovery reach for these particles and allow for studying their features, probing the lepton-flavour universality and constraining their Dirac or Majorana nature. In this talk, we will show how to look for HNL with masses above the Z-pole at future lepton colliders and answer the fundamental questions concerning their properties.

Speaker: Krzysztof Mekala

11:40 Searching for heavy neutral leptons through exotic Higgs decays at the ILC

In this study we investigate the feasibility of detecting heavy neutral leptons ($N_d$) through exotic Higgs decays at the proposed International Linear Collider (ILC), specifically in the channel of $e^+ e^- \to qq~ H$ with $H\to \nu N_d \to \nu~lW \to \nu l~qq$. Analyses based on full detector simulations of the ILD are performed at the center-of-mass energy of 250 GeV for two different beam polarization schemes with a total integrated luminosity of 2 $\mathrm{ab}^{-1}$. A range of heavy neutral lepton masses between the $Z$ boson and Higgs boson masses are studied. The $2\sigma$ significance reach for the joint branching ratio of $BR(H\to\nu N_d)\cdot BR(N_d\to lW)$ is about 0.1\%, nearly independent of the heavy neutral lepton masses, while the $5\sigma$ discovery is possible at a branching ratio of $0.3\%$. Interpreting these results in terms of constraints on the mixing parameters $|\varepsilon_{id}|^2$ between SM neutrinos and the heavy neutral lepton, it is expected to have a factor of 10 improvement from current constraints.

Speaker: Simon Thor

12:00 Collider phenomenology of the TeV-scale model with a common origin of neutrino mass, dark matter and baryon asymmetry

The origins of tiny neutrino mass, dark matter and baryon asymmetry of the Universe remain big mysteries in particle physics. To explain all these phenomena, a new physics model with a Higgs sector extended at the TeV scale was proposed by Aoki, Kanemura and Seto. However, CPV phases were neglected for simplicity, and the baryon number production via electroweak baryogenesis had not been evaluated. We have revisited this model including CPV phases and have investigated several phenomena including neutrino mass generation, dark matter relic abundance and electroweak baryogenesis. Future high-energy linear colliders are expected to play a crucial role in probing this model. In this talk, we will present some benchmark scenarios of the model where neutrino mass, dark matter and the baryon asymmetry can be simultaneously explained while satisfying all the theoretical and experimental constraints and discuss their predictions in future linear collider experiments.

Speaker: Kazuki Enomoto (Korea Advanced Institute of Science and Technology)

11:00 → 12:30 Conventional Facilities, Machine Detector interface: 2

11:00 A next generation, integrated community toolset for the modeling of linear colliders

The design of the next generation of linear colliders demands a renewed, high-performance, integrated set of simulation codes. We present the Beam, pLasma & Accelerator Simulation Toolkit (BLAST), which includes legacy accelerator codes such as Impact-T, Impact-Z, Warp and Posinst, as well as a renewed generation of accelerator codes such as ImpactX, WarpX and HiPACE++. The new codes, born out of the US DOE Exascale Computing Project (ECP), all share a common foundation based on the AMReX library that gives native support for mesh refinement and high performance on both CPU-based and GPU-based computer architectures. The integrated set also includes python-driven workflows for efficient parametric optimization and coupling with machine learning frameworks. We will present the latest of the toolkit and new codes, with examples and discussion on their applications to start-to-end modeling of linear colliders from the source to the interaction point beam-beam effects, whether using conventional radiofrequency or plasma-based acceleration technologies, or a combination.

Speaker: Jean-Luc Vay (Lawrence Berkeley National Laboratory)

11:20 Next-generation interaction point simulations for linear lepton colliders

The International Linear Collider (ILC) is among the most mature designs for a next-generation linear electron-positron collider. Plasma-based accelerators have also been proposed to reach the 10 TeV COM level further in the future. A key challenge in these types of machines is preserving the luminosity at the target value, mitigating the potentially detrimental effects of disruption, beamstrahlung, and background generation. This is why in-depth beam crossing studies are required to provide a comprehensive description of the physics at the interaction point. We present the exascale open-source code WarpX as a next-generation tool for beam-beam investigations. WarpX guarantees strong performance, portability (different operative systems, multi-CPU/GPU), flexibility (many options, algorithms, diagnostics, etc.), with up-to-date documentation and consistent maintenance within a large, active and multi-disciplinary community. We present benchmarks against established codes like GUINEA-PIG and CAIN, and show first results of simulation campaigns for the ILC, C^3, HALHF, and plasma-based colliders.

Speaker: Arianna Formenti (Lawrence Berkeley National Laboratory)

11:35 Beamstrahlung backgrounds in ILD at linear (ILC) and circular (FCCee) colliders

I will report on a comparison of beam-strahlung backgrounds at the ILC and FCCee, with an emphasis on the TPC and Vertex detector. The different MDI designs and beam timing structures at the two colliders have some dramatic effects on detector backgrounds.

Speaker: Daniel Jeans

11:50 Beam-Induced Backgrounds at the Cool Copper Collider

Beam-beam interactions constitute an important source of background at any electron-positron ($e^{+}e^{-}$) collider, generating the so-called beam-induced background (BIB), with important implications for the design and optimization of detectors at these machines and, ultimately, their physics reach. In this talk, we will present the latest results on the evaluation of the BIB at the Cool Copper Collider (C$^3$). We will begin with an overview of the various processes that contribute to the BIB at an $e^{+}e^{-}$ machine and evaluate their relative rates. We will then present simulation results for the production rates and kinematics of the dominant processes at C$^3$, namely incoherent $e^{+}e^{-}$ pair production and hadron photoproduction, and discuss technical challenges with these simulations, relevant for any $e^{+}e^{-}$ machine. Finally, utilizing full detector simulation for the SiD detector concept, we assess the impact of these backgrounds on the occupancy of the various sub-detector systems, most notably the vertex detector, and evaluate the effects of variations in the bunch time-structure of the beams. Our results indicate that C$^3$ background rates are compatible with the SiD concept and enable further beam parameter and detector optimizations in order to maximize the precision of important measurements at C$^3$.

Speaker: Dimitris Ntounis (SLAC National Accelerator Laboratory (US))

11:00 → 12:30 Higgs, Electroweak: 3

11:00 Searching for Charged Higgs Bosons via $e^+e^− \to H^+H^− \to c\bar b\bar cb$ at Linear Colliders

We study a search for the charged Higgs boson via $e^+e^− \to H^+H^− \to c\bar b\bar cb$ at the 500 GeV ILC. In a general two Higgs doublet model without $Z_2$ symmetry, extra Yukawa couplings $\rho_{tc}$ and $\rho_{tt}$ can drive electroweak baryogenesis, but searches at the HL-LHC may still go empty-handed if the couplings are relatively weak. Taking $m_{H^+} \simeq m_H \simeq$ $m_A\simeq 200$ GeV, with $\rho_{tc}, \rho_{tt} \sim 0.1$ and no $h(125)$-$H$ mixing, $H^+ \to c\bar b$ decay is dominant, and the $c\bar b\bar cb$ final state is likely overwhelmed by QCD background at the LHC. We show that the electroweak production of $H^+H^−$ at the ILC can be discovered with integrated luminosity of 1 ab$^{−1}$. Furthermore, we show that $m_{H^+}$ can be extracted by requiring the two pairs of $b$ and light jets be roughly equal in mass, without assuming the mass value. Thus, ILC can probe low mass Higgs bosons in multijet final states to complement HL-LHC in the future.

Speaker: George W.-S. Hou (National Taiwan University)

11:20 Impact of quark flavor violating SUSY on h(125) decays at future lepton colliders

We study the CP-even neutral Higgs boson decays h -> c \bar{c}, b \bar{b},
b \bar{s}, \gamma \gamma, g g in the Minimal Supersymmetric Standard Model (MSSM)
with general quark flavor violation (QFV) due to squark generation mixings,
identifying the h as the Higgs boson with a mass of 125 GeV. We compute the widths
of the h decays to c \bar c, b \bar b, b \bar s (s \bar b) at full one-loop level.
For the h decays to \gamma \gamma and g g we compute the widths at NLO QCD level.
For the first time, we perform a systematic MSSM parameter scan for these widths
respecting all the relevant theoretical and experimental constraints, such as those
from B-meson data, and the 125 GeV Higgs boson data from recent LHC experiments,
as well as the limits on Supersymmetric (SUSY) particle masses from the LHC experiments.
We also take into account the expected SUSY particle mass limits from the future HL-LHC
experiment. In strong contrast to the usual studies in the MSSM with Minimal Flavor
Violation (MFV), we find that the deviations of these MSSM decay widths from the
Standard Model (SM) values can be quite sizable and that there are significant
correlations among these deviations. Furthermore, we point out that the experimental
measurement uncertainties as well as the MSSM prediction uncertainties tend to cancel
out significantly in the width ratios, making the measurement of these width ratios
a very sensitive probe of virtual SUSY loop effects in these h decays at future lepton
colliders. All of these sizable deviations in the h decays are mainly due to large
scharm-stop mixing and large sstrange-sbottom mixing. Such sizable deviations from
the SM can be observed at high signal significance in future lepton colliders such
as ILC, CLIC, CEPC, FCC-ee and muon collider even after the failure of SUSY particle
discovery at the HL-LHC. In case the deviation pattern shown here is really observed
at the lepton colliders, then it would strongly suggest the discovery of QFV SUSY
(the MSSM with general QFV).
References:
Phys. Rev. D 91 (2015) 015007; JHEP 1606 (2016) 143; IJMP A34 (2019) 1950120;
PoS(ICHEP2022) 536; PoS(EPS-HEP2023) 487.

Speaker: Prof. Keisho Hidaka (Tokyo Gakugei University)

11:40 Towards an update of the ILD ZHH analysis

The double Higgs-strahlungs process ee -> ZHH allows to access the Higgs self-coupling at energies above ~450 GeV. It exhibits a very different BSM behaviour than fusion-type processes like gluon-gluon fusion at LHC (and future hadron colliders) and WW / ZZ fusion at higher energy lepton colliders. Therefore it adds unique information to the picture, in particular should the value of the Higgs self-coupling differ from its SM prediction. The last full evaluation of the ILC's potential to measure this process is more than 10 years old, and many of the reconstruction tools received very significant improvements since. This contribution will present the ongoing work in ILD to update the ZHH projections for the next European Particle Physics Strategy Update.

Speaker: Bryan Bliewert

11:55 Higher-order effects in the trilinear Higgs coupling for future collider experiments

Although the Higgs boson has been discovered, the couplings with the Higgs boson have room for deviation from the Standard Model (SM) prediction. Each extended Higgs model is characterized by its Higgs potential. Nearly aligned models where the shape of the Higgs potential is described by one classical field include the classical scale invariance model (CSI), the pseudo-Nambu-Goldstone model, the tadpole-induced model, and so on. This classification enables us to scrutinize numerous numbers of models efficiently by measuring the trilinear Higgs coupling with high precision. In this study, we calculate the trilinear Higgs couplings including loop contributions from the top quark and new particles for various Higgs potentials, and investigate the feasibility of future collider experiments. For several benchmark parameters, we show that the High-luminosity LHC and the ILC are capable of discriminating several extended Higgs models. We present the result of work in progress.

Speaker: Shuhei Ohzawa (University of Toyama)

12:15 Loop induced H±W±Z vertex in CP violating two Higgs doublet model and its impact on collider phenomenology

The two Higgs doublet model, which can serve enough CP violation and first order electroweak phase transition, is often introduced to realize electroweak baryogenesis.
If CP symmetry is violated in the two Higgs doublet model, it does not have custodial symmetry, which is remnant of global symmetry of SU(2)L × SU(2)R.
It has been known that H±W±Z vertex is induced at the loop level due to the violation of custodial symmetry.
As a consequence of breaking CP and custodial symmetry, we study loop-induced H± -> W±Z decay in the most general CP violating two Higgs doublet model.
In this talk, we discuss the relation between violations of CP and custodial symmetry and the H±W±Z vertex, and we show its impact on future colliders including ILC.

Speaker: Yushi Mura (Osaka Univ.)

11:00 → 12:30 Normal conducting RF: 3

11:00 HOM Detuning and Damping of C-Band Distributed Coupling Structure

Standing wave structures typically operate at the pi-mode. Evidently the cell length of such a structure is half a wavelength. However, maximal shunt impedance per unit length was found to be at a cell length of 3/8 wavelength, which corresponds to phase advance per cell of 135 degrees. A distributed coupling structure at 5.712 GHz was developed based on the high efficient 135/degree phase advance design. For practical linear collider designs, the structure must include HOM detuning and damping to mitigate long-range wakefields effects. Due to the high cutoff frequency of the cell iris, effective detuning and damping of the dipole HOMs at frequencies up to 40 GHz is required. In this presentation we will present HOM detuning and damping schemes to meet the long-range wakefield requirements of a linear collider design.

Speaker: Zenghai Li (SLAC)

11:20 A Wakefield Resilient, High Shunt Impedance Accelerating Structure for the Cold Copper Collider

The initial proposed design of the Cold Copper Collider (C3) is based on a distributed coupling accelerating (DCA) rf structure where the phase advance between the accelerating standing wave cavities is π. In these cavities the aperture radius is 2.624 mm and the corresponding shunt impedance is 300 MΩ/m with 77K copper walls. We propose a novel DCA rf structure with 3π/4 phase advance between the individually fed cavities aperture radius of 3.55mm for the same shunt impedance and the peak field constraints. Because of this 35% larger aperture, this rf structure is much more resilient to both short-range and long-range wakefield effects. The researchers at SLAC have already proposed and designed a 3π/4 DCA with four feeding waveguide manifolds. The implementation of four waveguide manifolds is, however, mechanically challenging. Here, we present a novel 3π/4 DCA for C3 which is based on only two waveguide manifolds. This rf structure comprises of 56 cavities where cavities are fed in pairs through a standard π phase advance rf manifold. This is achieved by pairing the cavities as, first and third, second and forth, and so on. With such pairing, the phase advance between the two cavities in a pair is π/2 and the phase advance between successive pairs is π. The copper cavities are designed to give a coupling coefficient of 1.82 at 77K temperature, as required for critical coupling to accelerate 190 mA with 70 MV/m gradient.

Speaker: Muhammad Shumail (SLAC)

11:40 Update on CARIE high gradient photocathode test stand at LANL

This talk will report on the status of commissioning of the Cathodes And Radio-frequency Interactions in Extremes (CARIE) high gradient C-band RF photoinjector test stand at Los Alamos National Laboratory. We are assembling and testing the high gradient photoinjector capable of producing electric fields at the cathodes up to 250 MV/m. The photoinjector will be powered by a 50 MW, 5.712 GHz Canon klystron. The klystron was delivered to LANL in July of 2023, installed, and commissioned. The waveguide line from the klystron goes through a high-power circulator into a concrete vault that is rated to provide radiation protection for electron beams with beam power up to 20 kW. The all-copper photoinjector was fabricated, tuned, and is awaiting high gradient testing. The second version of the photoinjector will be built with replaceable high quantum-efficiency cathodes to test behavior of advanced photocathode materials at high gradients. Adding capability to operate the photoinjector at cryogenic temperatures is considered. The status of the facility and its high-power operation and plans for photocathode testing will be presented.

Speaker: Evgenya Simakov (LANL)

12:00 Longitudinally-split side-coupled high-shunt-impedance C-band structure fabricated in two halves

Side-coupled structures operated with π/2 mode have been widely used particularly for compact linacs. The structure has various advantages; however, there are some difficulties in fabrication due to many complicated parts to be bonded in the conventional fabrication method. On the other hand, longitudinally-split structures are easy to fabricate due to the small number of parts (two halves or four quadrants). In recent years, in collaboration with Mitsubishi Heavy Industries, we have been developing longitudinally-split side-coupled C-band structure fabricated in two halves with a high shunt impedance based on our successful experience on the quadrant-type X-band CLIC prototype structure development. We report the status and results of this project.

Speaker: Abe Tetsuo (KEK)

11:00 → 12:30 Software, Reconstruction, Computing: 2

11:00 Classifying importance regions in Monte Carlo simulations with machine learning

In this work, we attempt to classify regions in a multidimensional parameter space according to their importance during a simulation. Considering that the parameter space could be high dimensional and the simulated process could result in arbitrary shapes, we involve a neural network in the process of guessing such shapes without running the full simulation for every point. We illustrate the process with a few examples, including scattering processes with several outgoing particles and compare with other known techniques for Monte Carlo simulations.

Speaker: Raymundo Ramos (Korea Institute for Advanced Study)

11:20 Development of particle flow algorithm with GNN for Higgs factories

Particle flow plays an important role in precise measurement of Higgs bosons at future lepton colliders such as ILC and FCCee. Various detector concepts are designed to maximize the effect of particle flow to be able to separate each particle s inside jets and improve the resolutions. For the standard particle flow algorithm, PandoraPFA is used for long in ILC studies. It is a multi-step reconstruction algorithm consisting of clustering, track-cluster association, and various refinement processes. We have studied machine learned particle flow model using Graph Neural Network based algorithm developed in the context of CMS HGCAL clustering. This model utilizes GravNet as GNN architecture and Object Condensation loss function for training. Since the HGCAL algorithm only performs clustering at the calorimeter, we developed track-cluster matching feature inside the network to realize full PFA. Details of initial implementation of the track-cluster matching algorithm as well as performance evaluation with multiple tau events and jet vents will be shown. We also report the comparison result between computational performance of the machine learned algorithm and the PandoraPFA.

Speaker: Tatsuki Murata

11:40 Impact of NLO QCD on Key Physics Processes at Future Higgs Factories

The majority of Monte-Carlo (MC) simulation campaigns for future Higgs factories has so far been based on the leading-order (LO) matrix elements provided by Whizard 1.95,
followed by parton shower and hadronization in Pythia6,
using the tune of the OPAL experiment at LEP.
In this contribution, we test the next-to-leading-order (NLO) mode of Whizard.
NLO events of $e^+e^-\to q\bar{q}$ and $e^+e^-\to \mu^+\mu^-b\bar{b}$ are generated by POWHEG matching,
with parton shower and hadronization provided by Pythia8.
The NLO effect on hadron multiplicities and event shape variables of jets will be
discussed and compared with MadGraph5 at hadron-level.
After passing the events through the full detector simulation of the
International Large
Detector concept as an example for a ParticleFlow-optimised detector,
the jet energy
resolution and typical kinematic quantities are compared between NLO and
LO at reconstruction level.
A first assessment of which physics prospects of future $e^+e^-$ should be
studied with NLO MC in the future will be given.

Speaker: Zhijie Zhao (DESY)

11:00 → 12:30 Sources: 3

11:00 Present status and plan on E-driven positron source for ILC

Present status and plan on E-driven positron source for ILC　will be presented.
This talk might be a introduction to the several related topics by colleagues working on the project.

Speaker: Dr yoshinori enomoto (KEK)

11:20 Design of the ILC electron-driven positron source and utilization of black-box optimization

The International Linear Collider (ILC) represents the next generation of electron-positron colliders, designed to operate at center-of-mass energies ranging from 250 GeV, with plans to extend up to 1 TeV in the future. This opens up a broad spectrum of possibilities for exploring physics beyond the Standard Model. The ILC requires advanced engineering technology and meticulous design to generate large quantities of positrons. In the design of the ILC electron-driven positron source, simulation tools such as Geant4, GPT, and SAD are employed. In a significant shift from the previous human-intensive, step-by-step optimization procedures, we have now embraced black-box optimization methods, including Bayesian optimization, to streamline and enhance the parameter optimization of the positron source accelerator system. This methodological evolution has not only boosted efficiency but also redirected more resources towards further design improvements. By incorporating machine learning techniques from the initial stages of accelerator design, we anticipate the development of accelerators that are not only more efficient but also significantly more precise. Here, we present the current status of the ILC electron-driven positron source and its design methodology.

Speaker: Shunpei Kuroguchi (Hiroshima U.)

11:40 Development of E-driven positron target.

Development of E-driven positron target.

Speaker: Mr Yu Morikawa (KEK)

12:00 APS cavity design for ILC E-driven positron capture linac

We present the design of an APS cavity for the capture linac of the ILC E-driven positron source.　It is required to accelerate a high-current multi-bunch positron beam in this positron source. Therefore, beam loading compensation and managing the heat load exceeding 10 kW due to electromagnetic showers generated at the target are important issues. We have designed a 21-cell APS accelerator, comprising 11 accelerating cells and 10 coupling cells with sufficient space for cooling channels. This presentation will report on the current status of the APS cavity design.

Speaker: Masafumi Fukuda (KEK: High energy accelerator research organization)

11:00 → 12:30 Superconducting RF: 4

Convener: Dimitri Delikaris (CERN)

11:00 High pressure gas safety and cavity performance in MEXT-ATD/ITN

MEXT-ATD/ITN cavities will be fabricated under the high-pressrue gas safety (HPGS) act, refregeration safety regulations. Mechanical test for all the material and stress analysis of ITN/TESLA cavity were performed. Application documents are almost ready for submission. Presentation is given for the status of HPGS application, including proposal of cavity surface treatment.

Speaker: Kensei Umemori (KEK)

11:20 Cryomodule Test Buncer for ITN

ITN is an acronym for "ILC Technology Network".
It is an international framework for the technological development outlined in the Work Package(WP).
KEK plans to produce one cryomodule equipped with eight superconducting 9-cell cavities for WP1 and 2 from 2023 and perform performance measurements in 2027.
A test facility will be required to perform the measurements.
We are preparing the cryogenics for the facility.
The refrigerator (Linde LR280) currently operating at KEK will be dedicated to that.
The helium transfer line was designed.
The design was based on KEKB's transport line design, but it was slightly modified because ILC does not use liquefied nitrogen for the radiation shield.
The 2K refrigerator, purification filter, and other equipment are also considered. We will report on the status of those.

Speaker: Kota Nakanishi (KEK)

11:40 Cryomodule design and construction at KEK

KEK is now constructing a cryomodule for 1.3 GHz TESLA cavities. Design of this cryomodule and the status of construction will be presented in this talk.

Speaker: Takeshi Dohmae

11:55 Towards field emission free cavity processing and string assembly at Fermilab

Cavities and cryomodules assembled at Fermilab have demonstrated unprecedented field emission (FE) free gradients. However, consistent FE-free performance is not guaranteed. Many lessons were learned, and continued vigilance is a must. In addition, several improvements have been identified to further push the state-of-the-art low particulate cavity processing and assembly at Fermilab. Those included the optimization of nitrogen flow, robotic-assisted assembly, and low-particulate fasteners. We share our latest results and vision for the future clean assemblies of cavities and cryomodule strings.

Speaker: Genfa Wu

12:15 The status of robotic clean assembly in KEK

Robotic dust-free clean assembly is currently attracting worldwide　attention, and KEK has purchased a Fanuc CRX-20iA/L and is conducting R&D for its application to ILC type string assembly. The status of KEK's　activity on the robotics will be presented in the presentation.

Speaker: Tomohiro Yamada (KEK)

12:30 → 14:00 IDT-WG3 steering group (closed)

https://agenda.linearcollider.org/event/10384/

Speaker: Jenny List (Deutsches Elektronen-Synchrotron (DE))

12:30 → 14:00 Lunch

14:00 → 15:30 Advanced Accelerator Concepts: 2

14:00 Application of laser-plasma accelerators to future linear colliders

Laser-driven plasma accelerators have demonstrated ultra-high accelerating gradients, offering the potential to reduce the size and cost of a future energy-frontier linear collider. In this presentation, I will discuss the design considerations for the application of laser-driven plasma-based accelerator technology to a multi-TeV linear collider. Plasma accelerators naturally accelerate short bunches using large longitudinal and transverse wakefields in plasma, and this presents unique beam dynamics challenges. I will discuss several of these challenges, including staging laser-plasma accelerators, scattering with background plasma, and beam transverse stability. Key to the realization of the collider application is the development of high average and high peak power laser systems, operating with high efficiency. Coherent combination of fiber lasers is a promising solution to achieve high average and high peak power lasers suitable for high-energy physics applications, and I will describe recent progress and outline the R&D path toward a collider based on laser-plasma accelerator technology.

Speaker: Carl Schroeder (LBNL)

14:15 Simulation studies towards HEP applications of plasma accelerators

Plasma accelerators sustain large field gradients and could enable future x-ray sources and compact linear colliders. The development of performant open-source simulation methods allows for the investigation of open challenges towards these applications, including the acceleration of beams with high quality to high energies. This presentation will discuss recent studies on these topics.
First, we will discuss the possibility to use a laser-plasma accelerator as an injector for the next-generation storage ring Petra IV at DESY. This requires several nanocoulombs of 6-GeV electrons per second with a sub-percent energy acceptance, and an energy compression beamline was developed to fulfil these requirements. A Conceptual Design Report will be published soon.
Second, to achieve the required high luminosity, linear colliders rely on flat beams to avoid potentially deleterious beamstrahlung effects. We show that flat beams in plasma accelerators can be subject to beam quality degradation due to emittance mixing caused by transverse coupling in the wakefields. Depending on the mechanism causing the resonance, the use of laser drivers, flat particle beam drivers, or hollow plasma channels can avoid the resonance and mitigate the emittance deterioration.

Speaker: Maxence Thévenet (DESY)

14:30 Advanced structures R&D for structure wakefield acceleration at the Argonne Wakefield Accelerator

Research and development on novel structures is at the core of advancing structure wakefield acceleration (SWFA), and is critical to future AAC-based linear colliders. In this talk, I will present recent progress on the R&D of advanced radiofrequency (RF) structures for Structure Wakefield Acceleration, metamaterial structures, and sub-terahertz structures. The experiments were performed at the Argonne Wakefield Accelerator (AWA) facility, where we capitalized on the capability of generating shaped-electron bunches to improve SWFA performance.

Speaker: Xueying Lu (Northern Illinois University / Argonne National Lab)

14:45 Progress of research on corrugated wakefield structures in PAL working group.

Our research group, composed of Pohang Accelerator Laboratory, Korea University, Northen Illinois Universiy, and Argonne Wakefield Accelerator Facility, is researching on wakefields generated in corrugated structures. Main goal of our research is to make several applications such as a THz source in the GW scale, wakefield accelerators and IR-FELs.
As a first step, we designed and fabricated structures in the 200 GHz frequency range, and their performance were validated by the experimental results in AWA. In the first experiment, even with a fabrication tolerance of around 10 micrometers, the simulation results matched well with the experimental results. We are developing more precise fabrication methods by lithography for higher output power and frequency. As the second step, we are preparing to fabricate corrugated structures around 425 GHz and demonstrate GW-level THz output.

Speaker: Hyung-sup Kong (Pohang Accelerator Laboratory)

15:00 Advancements in Beam Delivery Systems: CLIC Innovations and Plasma Collider Applications

This talk presents the latest developments in beam delivery systems (BDS) for the Compact Linear Collider (CLIC) and their applications in plasma colliders. The CLIC's BDS has undergone significant refinements to address challenges in minimizing beam size, correcting chromatic aberrations, and maintaining stability at high energies (380 GeV and 3 TeV). Key innovations include the integration of detector solenoid effects and the implementation of a dual BDS concept. This concept effectively manages larger crossing angles and the associated luminosity losses, which are critical at energies up to 3 TeV. Furthermore, the extension to a proposed 7 TeV CLIC BDS design anticipates the requirements of future colliders, focusing on trajectory bending minimization and chromaticity correction. Collaborations with plasma collider projects like Laser Plasma Accelerators (LPA) and Hybrid, Asymmetric, Linear Higgs Factory (HALHF) highlight synergistic solutions to shared technical challenges, notably in emittance preservation and energy spread control. These collaborations are pivotal in advancing the understanding of beam dynamics and delivery, setting a robust foundation for next-generation particle collider designs.

Speaker: Vera Cilento (CERN)

15:15 High energy plasma injector for future electron-positron collider

The next generation electron-positron collider is crucial for precision measurements of the Higgs boson and exploring new physics beyond the Standard Model. Currently, the scale and cost of linear or circular colliders based on traditional radio-frequency accelerators are enormous to meet the standards for a Higgs factory. Advanced accelerator concepts such as the plasma wakefield accelerator (PWFA) can provide acceleration gradient orders of magnitude higher than RF cavities, which may greatly reduce the scale and cost of these facilities. At present, the state-of-the-art developments for these schemes fall short of achieving the beam parameters required by the collider. We propose a hybrid electron-positron collider scheme which uses PWFA as a high energy injector for the future collider. The plasma wakefield accelerators greatly boost the energy of the electron and positron beams from the RF Linacs by multiple times before injecting them into the booster or collider rings. Nearly start-to-end numerical simulations show that the final beam parameters of the electron and positron beams fulfill the requirements of the booster. The developments in this scheme can be a significant middle step towards the future plasma based linear colliders.

Speaker: Shiyu Zhou (Tsinghua University)

14:00 → 15:30 Applications: 1

14:00 Probing non-perturbative QED and new physics in laser-particle beam collisions at LUXE and prospects for a future Higgs factory

The proposed LUXE experiment (Laser Und XFEL Experiment) at DESY, Hamburg, using the 16.5 GeV electron beam extracted from the European XFEL, aims to study collisions between high-intensity laser pulses and high-energy electron or secondary photon beams (unique feature at LUXE). This will elucidate quantum electrodynamics (QED) at the strong-field frontier, where the electromagnetic field of the laser in the probe particle rest frame is above the Schwinger limit. In this regime, QED is non-perturbative. This manifests itself in the creation of physical electron-positron pairs from the QED vacuum, similar to Hawking radiation from black holes. LUXE intends to measure the positron production rate in an unprecedented laser intensity regime. The strong-field QED effects probed by LUXE are expected to become relevant for beam-beam interactions at future electron-positron colliders. The LUXE setup also provides a unique opportunity to probe physics beyond the standard model by impinging the large photon flux from Compton scattering onto a beam dump, thereby probing axion-like-particles (ALPs) at a reach comparable to FASER2 and NA62. Furthermore, the extracted 16.5 GeV EuXFEL electron beam for LUXE can be used for studies of plasma boosting for plasma-enhanced future electron-positron collider concepts, such as HALHF.

In this contribution we will give an overview of the LUXE experimental setup and its challenges, as well as its implications for future electron-positron colliders. Finally, we discuss the prospects of a high-energy extracted electron beam facility for future collider developments and explore the potential of a LUXE-type experiment at a future Higgs factory.

Speaker: Ruth Magdalena Jacobs (Deutsches Elektronen-Synchrotron (DE))

14:30 The alignment of the modules of the Cool Copper Collider (C^3) with the Rasnik 3-point alignment system

For C^3, approximately 2000 accelerator sub units must be positioned, within 10 um transversal, on a 2.3 km long straight line for each linac.
In the Rasnik alignment system, light from a point-like monochromatic source falls on a zone plate, forming a Fraunhofer diffraction pattern on an image pixel sensor. The alignment of three objects can be obtained by analyzing the position of the diffraction pattern on the sensor.
The alignment of a large number of objects can be realized by fixing a stick on each object, carrying the three Rasnik components. With this leap frog geometry, all sticks are mutually coupled, forming a multipoint alignment system [1].
This system should operate in ambient air, in vacuum, and in liquid nitrogen. Usable low-cost laser diodes that operate in these conditions have been found, as well as one type image pixel sensor, applied in an old Microsoft webcam. Due to the heat dissipation of these components, bubbles are formed, causing an error in the measured alignment when crossing the optical path. Various methods of beam shielding are presented.
With the Quarter Cryo Module (QCM), essential studies will be carried out, enabling the realization of the C3 collider. The QCM will be equipped with four Rasnik chains, measuring alignment parameters with redundancy. In addition, the bubble-induced vibrations of the accelerator components can be registered accurately.

[1]  H. van der Graaf et al., The alignment of the C3 Accelerator Structures with the Rasnik alignment system. Proceedings of LCWS 2023. arxiv: 2307.07981

Speaker: Harry Van Der Graaf (Nikhef National institute for subatomic physics (NL))

15:00 Compact Traveling Wave X-band Linac with RF Power Flow Outside Accelerating Cavities

During the development of the NLC/JLC normal conducting X-band linear colliders, it became clear that the RF power flow in traveling wave accelerating structures correlates more with the RF breakdown rate than with the peak electric fields. To mitigate the adverse effects of RF power flow, low group velocity and standing wave accelerating structures optimized for lower RF input power have been developed. As an alternative, to avoid RF power passing through the accelerating cavities, a new traveling wave structure was invented. Since this structure has higher efficiency than traditional axially coupled accelerator structures, it can be used in compact linear accelerators. In this report, we present a compact X-band linac that uses this new accelerating structure.

Speaker: Valery Dolgashev (SLAC National Accelerator Laboratory)

14:00 → 15:40 BSM, Global Interpretations: joint with HiggsEW

14:00 Overview on low mass scalars at e+e- facilities - theory

Many new physics scenarios render a low mass scalar candidate. I will briefly discuss the current status of such models, and give an short overview on current studies for such models at Higgs factories, including efforts within the ongoing ECFA effort.

Speaker: Tania Natalie Robens (Rudjer Boskovic Institute (HR))

14:20 The 95 GeV Higgs at $e^+e^-$ colliders

Several searches for Higgs bosons below 125 GeV show an excess around $m_\phi = 95.4$ GeV. These include in particular $gg \to \phi \to \gamma\gamma$ at CMS and ATLAS and $e^+e^- \to Z^* \to Z (\phi \to b \bar b)$ at LEP. We discuss BSM Higgs sectors that can accommodate these excesses. We demonstrate that such a light Higgs boson can be analyzed in detail at $e^+e^-$ colliders.

Speakers: Georg Ralf Weiglein (Deutsches Elektronen-Synchrotron (DE)), Sven Heinemeyer (Consejo Superior de Investigaciones Cientificas (CSIC) (ES))

14:40 A BSM world with doubly charged scalars. Consequences for e+e- projects.

In the recent years a large set of indications for BSM scalars has been observed in LHC data. After a brief description of the most significant indications, this presentation intends to give a consistent interpretation in terms of a generalised Georgi Machacek model which predicts a doubly charged scalar indicated by ATLAS data. Consequences for currently planned e+e- colliders will be sketched. An updated description of this work can be found in Arxiv 2308.12180.

Speaker: Dr Francois Richard (IJCLAB)

15:00 Prospects for light exotic scalar measurements at the e+e- Higgs factory.

The physics program of the Higgs factory will focus on measurements of the 125 GeV Higgs boson, with the Higgs-strahlung process being the dominant production channel at 250 GeV. However, production of extra light scalars is still not excluded by the existing experimental data, provided their coupling to the gauge bosons is sufficiently suppressed. Fermion couplings of such a scalar could also be very different from the SM predictions leading to non-standard decay paterns. Considered in the presented study is the feasibility of direct light scalar observation at future Higgs factory experiments assuming different decay channels.

Speaker: Aleksander Filip Zarnecki (University of Warsaw)

15:20 Feasibility study on the search for an exotic decay of the Higgs boson into two light pseudoscalars in e+e- collider

A feasibility study is conducted to search for an exotic decay of the Standard Model Higgs boson decaying into a pair of light pseudoscalar bosons in the Cool Copper Collider (C3) experiment. The Higgs boson is produced in association with a Z boson and the decay products consist of a pair of b-quarks and tau leptons. The pseudoscalar bosons are probed over a mass range spanning from 20 to 60 GeV. A simplified algorithm is devised to reconstruct the tau lepton in its hadronic decay mode. A limit on the branching ratio of the Higgs boson to a pair of light pseudoscalars is presented assuming 1 fb-1 of data.

Speaker: CHENG-HSU NEE (UW-Madison)

14:00 → 15:30 Beam Dynamics: 2

14:00 Update of the CLIC RTML

The CLIC RTML was simulated and optimised for the 380 GeV energy stage. Some remaining problems in the RTML design were solved and the baseline design was finalised. The cost for the BC2 and the bunch phase shift effect were minimised.Static imperfections were studied with the emittance budget well achieved after BBA corrections. Jitter amplification was also studied. The possibility of using X-band or C-band booster linac was also studied.

Speaker: Yongke Zhao (CERN)

14:20 Emittance tuning knobs for the Main Linac of CLIC 380 GeV

The high luminosity specifications for future linear colliders, such as the Compact Linear Collider (CLIC), require extremely small vertical beam emittance at the interaction point. Achieving this relies on minimizing the emittance growth in the collider sub-systems. One major source of emittance growth is in the Main Linac, mainly due to misaligned quadrupoles and accelerating structures. The current budget for normalized emittance growth is 5 nm for static misalignments and another 5 nm for dynamic imperfections. The budget for the static imperfections is achieved through the use of beam-based alignment, such as one-to-one correction, dispersion-free steering, and the realignment of accelerating structures. In this work, we explore the use of additional emittance tuning bumps to further decrease the emittance growth and to provide additional leverage for the tuning.

Speaker: Mr Andrii Pastushenko (CERN)

14:40 Design and optimization of the Final Focus System for 7 TeV Compact Linear Collider

The Compact Linear Collider (CLIC) proposes a linear accelerator system aimed at colliding electrons and positrons at energies up to 3 TeV. To explore novel physics and enhance competitiveness with other collider projects, CLIC is considering increasing the center-of-mass energy to 7 TeV. A crucial component of the CLIC infrastructure is the Beam Delivery System (BDS), responsible for transporting lepton beams from the Main Linac exit to the Interaction Point (IP). This paper presents an overview of the studies and challenges associated with the design of the new Final Focus System (FFS), such as implementing chromaticity correction to mitigate synchrotron radiation effects, and ensuring precise transverse aberration control at the IP.

Speaker: Enrico Manosperti (Universitat Politecnica Catalunya (ES))

14:00 → 15:30 Software, Reconstruction, Computing: 3

14:00 Finding kink signatures of LLPs in TPC at ILC

Some types of LLPs can be indentified by kinked tracks. The Time Projection Chamber (TPC) being designed for ILD at ILC provides almost continuous tracking. This should give excellent potential for kink finding. I will review the current kink finder algorithm, and present a new kink finding method.

Speaker: Jurina Nakajima (SOKENDAI/KEK)

14:20 Towards production readiness with the Key4hep software stack for future colliders

Physics studies for future colliders require a reliable software environment. For many years this has been delivered by iLCSoft for the linear collider communities. In the last five years a common effort of several communities, including ILC, CLIC, FCC and CEPC, have collaborated on the Key4hep software stack to deliver a common software stack for all future collider communities. This software stack has been used for physics studies already and is reaching production readiness.

This presentation an overview of the current status of Key4hep, giving special emphasis on the developments that are particularly relevant for the linear collider communities. We will show the seamless integration of existing reconstruction and analysis software that have been developed in the last 15 years by the linear collider communities. Additionally, we will lay out the path forward from a software perspective and report on experiences from migrating the standard ILD reconstruction chain towards Key4hep. Additionally, we show some new developments for ILD that are currently ongoing within Key4hep. Finally, we report on currently ongoing developments and future plans.

Speaker: Thomas Madlener (Deutsches Elektronen-Synchrotron (DE))

14:40 Fast Timing for Particle ID

The identification of certain charged hadron species, e.g. Kaons and protons, plays an important role in many physics analyses. Time-of-flight measurements can contribute to identifying these particles if both the length of the flight path as well as the time of arrival can be determined with sufficient precision. This contribution will discuss the recent progress on both aspects, and in particular compare classic as well as machine-learning based algorithms in order to estimate the time-of-arrival at the calorimeter front from the time measurements of individual hits in a shower or MIP trace.

Speaker: Jenny List (Deutsches Elektronen-Synchrotron (DE))

14:00 → 16:00 Superconducting RF: 5

Convener: Daniele Sertore (INFN Milano - LASA)

15:00 Plasma processing development for SPIRAL2 quarter-wave resonators: experimental and simulation studies

Plasma processing stands as an in-situ technique for mitigating field emission and multipacting effects in the long-term operation of superconducting accelerating cavities. While extensively explored and applied to elliptical cavities, its application to quarter-wave resonators (QWRs) represents a relatively recent area of investigation. At IJCLab, ongoing efforts focus on refining plasma processing techniques tailored for SPIRAL2 QWRs. This talk will center on our experimental findings, compared with numerical simulations of a simplified system featuring 2D axisymmetric geometry and employing a basic plasma chemistry composed of pure argon, instead of Ar/O2(10%). This strategic simplification makes it possible to reduce the calculation time while also providing an understanding of the dynamics of the plasma within the cavity. The simulations have been conducted using COMSOL Multiphysics.

Speaker: Camille Cheney (IJCLAB)

15:20 Robotisation of cavity string assembly at CEA

Since 2017, CEA has been developing the use of collaborative robots (cobot) to carry out the steps required to assemble superconducting cavities strings. This development is based on two main objectives. The first is to reduce the tediousness for operators of certain stages of component cleaning by blowing, so that they can focus on higher value-added tasks. The second is to improve assembly quality by keeping operators, the main sources of particle contamination in cleanrooms, away from open critical RF surfaces. The integration of component cleaning (flange, inter-cavity bellows, etc.) in the cleanroom by the cobot was carried out on the production of ESS cryomodules cavity strings. For future projects, CEA is currently working on the cobotisation of component assembly steps to meet the second objective.

Speaker: Julien Drant (CEA Saclay, IRFU)

15:40 Status of ess cryomodule test in orepararion for beam commissioning

ESS is completing the installation of the first phase of the operation, which will start in the fall of 2024 on the partial beam dump and proceed with operation on the target in 2025, after receiving the intentional neutron production license from the authorities.
All modules (CM) for this operation phase, with an energy reach of 870 MeV and a power capability of 2 MW, will be tested by early summer 2024.
Site Acceptance test of ESS elliptical modules takes place at TS2, Lund ESS Test Stand, and all module performance data is stored. Along with cavity conditioning in an open loop and cavity operation in a closed loop, field emission maximum energy and both gamma and neutron dose rates are measured and stored.

The CM performance, associated statistics, operational experience and challenges is discussed here.

Speaker: Cecilia Maiano (ESS)

14:00 → 15:30 Top, QCD, Flavor, Precision Modelling: 3

14:00 The new Sherpa 3.0 event generator

Accurate and fully differential predictions are crucial inputs for the precise experimental analyses at linear colliders and are typically provided by parton shower Monte Carlo programs. The event generator Sherpa with its focus on the inclusion of higher-order EW and QCD effects is available in a new version 3.0 this year and we will summarise its new features in particular where they relate to linear colliders.

Speaker: Frank Siegert (Technische Universitaet Dresden (DE))

14:30 New developments in the Whizard event generator

We give a status report on new developments within the WHIZARD event generator. Important new features comprise NLO electroweak automation (incl. extension to BSM processes like SMEFT), loop-induced processes and new developments in the UFO interface. We highlight work in progress and further plans, such as the implementation of electroweak PDFs, photon radiation, the exclusive top threshold and features for exotic new physics searches.

Speaker: Jürgen Reuter (DESY Hamburg, Germany)

15:00 The Alaric parton shower algorithm

Parton showers are important tools in the event generation chain for future collider. Recently, their formally achieved accuracy has been under extended scrutiny. In this talk I will present a novel take on dipole parton showers [1], resulting in the design of a new parton shower called Alaric that is implemented in the Sherpa framework. I will discuss its resummation properties and show analytic and numerical proofs of its NLL accuracy. I will discuss the latest developments, see [2], and their implications for final state evolution.

[1] JHEP 10 (2023) 091
[2] arXiv:2404.14360

Speaker: Daniel Reichelt

15:30 → 16:30 EAJADE: by invitation

Conveners: Steinar Stapnes (CERN), Thomas Schoerner-Sadenius (Deutsches Elektronen-Synchrotron (DE))

15:30 → 16:00 coffee

16:00 → 17:30 Applications: 2

16:00 High-Gradient X-band Linac for Direct Electron Radiation Therapy

We report on cold test measurements of an X-band (11.424 GHz) accelerator to provide electron beams for Very High Energy Electron therapy of cancer. The standing wave linac is designed with a 135° phase advance utilizing distributed coupling through four parallel manifolds. The accelerator is expected to reach a 100 MeV/m accelerating gradient in a one-meter structure using only 19 MW when operating around 77 K. We will present measurements from a clamped benchtop test at room temperature of the assembled linac plates prior to bonding. These fabricated prototypes will be diffusion bonded.

Speaker: Emma Snively (SLAC National Accelerator Laboratory)

16:30 Modeling and Design of the SLAC 75XP4 Klystron

The SLAC 75XP series klystron was developed in the late nineties / early 2000’s as a 60% efficient, 75 MW permanent magnet-focused klystron at X-band for the Next Linear Collider (NLC). SLAC is pursuing the latest design iteration of the 75XP series – the 75XP4 - for potential deployment in future colliders facilities like Cool Copper Collider. Here, we discuss the history and lessons learned from the initial 75XP klystrons (75XP1 through 75XP3 series). Recent design modifications for the 75XP4 and simulation results will be discussed. Finally, a status update of SLAC’s current efforts to build and test an improved 75XP4 version will be presented.

Speaker: Brandon Weatherford

16:00 → 17:30 Calorimetry, Muon detectors: 3

16:00 Longitudinal structure optimization for the high density electromagnetic calorimeter

High density electromagnetic sandwich calorimeters with high readout granularity are considered for many future collider and fix-targer experiments. Optimization of the calorimeter structure from the point of view of the electromagnetic shower energy, position and direction measurement is one of the key aspects of the design. However, mostly uniform sampling structures were considered so far. We developed a semi-analytical approach to study calorimeter performance based on the detailed Geant 4 simulation, which also allows to compare the expected performance for different non-uniform longitudinal readout structures. This methodology enables us to find out the best calorimeter instrumentation pattern upon a specified usage scenario or optimization goal.

Speaker: Aleksander Filip Zarnecki (University of Warsaw)

16:20 The SiD Digital ECal Based on Monolithic Active Pixel Sensors

Unprecedented precision is needed to address the Higgs physics with detectors at future e+e- colliders. Linear colliders offer low duty cycles and low backgrounds, that greatly assist achieving these goals. The SiD Collaboration is developing an application of Monolithic Active Pixel Sensor (MAPS) technology for tracking and electromagnetic calorimetry (ECal). This technology offers high granularity, thin sensors, fast responses ($<$nsec), and small dead areas. The low collider duty cycle enables gaseous cooling for tracking and passive heat removal for calorimetry.

A MAPS prototyping effort (NAPA-p1) is led by SLAC in collaboration with CERN. This is aimed at the linear collider tracking requirements, with complementary application to the ECal requirements. The device testing status is covered in an abstract submitted to the LCWS "Vertex, Tracking, Timing" track. This calorimetry talk will briefly summarize that work, and concentrate on the ECal design and system level considerations, as well as the ECal performance simulations.

Small pixels significantly improve shower separation in the ECal. Detailed simulation of ECal performance confirms previous results, indicating electromagnetic energy resolution based on digital hit cluster counting provides better performance than the 13 mm$^2$ pixels SiD TDR analog design. Furthermore, two particle separation in the ECal is excellent down to the millimeter scale. Geant4 simulation results with optimized analysis based on machine learning has been studied to optimize these expectations.

Speaker: Jim Brau (University of Oregon (US))

16:40 Metrology in the integrated luminosity measurement at ILC

Possibility that the ILD detector might be realized at a future e+e- collider calls for quantification of precision of the integrated luminosity measurement, assuming here the ILC operating scenarios at the Z-pole, 250 GeV, 500 GeV and 1 TeV center-of-mass energies. This is the first comprehensive study of the systematic uncertainties in integrated luminosity measurement at ILC, rising from metrology (detector positioning and alignment, beam properties and delivery to the IP), after the generic estimates given in LC-DET-2005-004.

Speaker: Dr Ivan Smiljanic (VINCA Institute of Nuclear Sciences, University of Belgrade (RS))

17:00 Monte Carlo Simulations of an electromagnetic sampling calorimeter with semiconductor sensors

The simulation of particle generation, their interaction with detector materials, and the resulting detector response has become increasingly crucial in recent experiments. Semiconductor+W calorimeters, known for their high compactness and granularity, are integral components of proposed detector designs for upcoming Higgs Factories as well as experiments targeting strong-field-QED (LUXE) or forthcoming smaller-scale experiments. This contribution focuses on optimizing the ECAL electromagnetic calorimeter, foreseen to the LUXE experiment to achieve higher energy resolution, using a Geant4-based application. Additionally, a fundamental aspect of this effort involves simulating the responses of Si or GaAs -type sensors. This simulation not only contributes to the initial detector design but also serves as an indispensable tool for predicting the detector’s performance. Incident electrons with energies ranging from 2.0 to 18.0 GeV were directed towards ECAL surface, their interactions with materials assesed and the results are presented. Furthermore, detailed configurations of the sampling electromagnetic calorimeter and the Geant4 simulation package are discussed.

Speaker: Petru-Mihai Potlog (Institute of Space Science - Subsidiary of INFLPR)

16:00 → 17:30 Conventional Facilities, Machine Detector interface: 3

16:00 Beam backgrounds at HALHF

The Hybrid Asymmetric Linear Higgs Factory (HALHF) proposes a shorter and cheaper alternative for a future Higgs factory. The design includes a 500 GeV electron beam accelerated by an electron-driven plasma wake-field, and a conventionally-accelerated 31 GeV positron beam. Assuming plasma acceleration R&D challenges are solved in a timely manner, the asymmetry of the collisions brings additional issues regarding the detector and the physics analyses, from forward boosted topologies and beam backgrounds. This contribution will detail the impact of beam parameters on beam-induced backgrounds, and provide a first look at what modification to e.g. the ILD can improve the physics performance at such a facility. The studies are benchmarked against some flagship Higgs Factory analyses for comparison.

Speaker: Antoine Laudrain (Deutsches Elektronen-Synchrotron (DE))

16:15 Status of FCC civil engineering and site investigations

Following the mid-term review in 2023, the Future Circular Collider (FCC) feasibility study at CERN continues towards the European Strategy for Particle Physics 2025. This talk will cover the main updates, current progress of the civil engineering design and the status of the geotechnical site investigations.

Speaker: Liam Bromiley (CERN)

16:35 Study status of Beam Backgrounds and MDI Design at the CEPC

The machine-detector interface (MDI) issues are one of the most complicate and challenging topics at the Circular Electron Positron Collider (CEPC). Comprehensive understandings of the MDI issues are decisive for achieving the optimal overall performance of the accelerator and detector. The machine will operate at different beam energies, therefore, a flexible interaction region design will be plausible to allow for the large beam energy range. The design has to provide high luminosity that is desirable for physics studies, but keep the radiation backgrounds tolerable to the detectors. This requires careful balance of the requirements from the accelerator and detector sides.
In this talk, the latest design of the CEPC MDI based on CEPC Technical Design Report (TDR) will be presented, covering the design of the beam pipe and whole IR, the estimation of beam induced backgrounds, the mitigating schemes, and also our plan towards the Ref-TDR of CEPC detector and EDR of accelerator.

Speaker: Haoyu Shi (Institute of High Energy Physics, Chinese Academy of Sciences)

16:50 MDI at gamma gamma collider

MDI at gamma gamma collider

Speakers: Tim Barklow (Stanford Linear Accelerator Center SLAC), Tim Barklow (SLAC National Accelerator Laboratory (US))

16:00 → 17:30 Damping rings, Beam delivery systems: 2

Convener: Andrea Latina (CERN)

16:00 State of the art in low-emittance storage rings and CLIC DR design

State of the art in low-emittance storage rings will be presented.

Speaker: Yannis Papaphilippou (CERN)

16:15 Present design of ILC DR

The present design of ILC DR will be presented.

Speaker: Kiyoshi Kubo (KEK)

16:30 Status and plans for ILC BDS

The current status and future development plans of ILC BDS will be explained.

Speaker: Toshiyuki Okugi (KEK)

16:45 Status and plans of CLIC BDS

Status and plans of CLIC BDS will be presented.

Speaker: Enrico Manosperti (Universitat Politecnica Catalunya (ES))

17:00 ATF2 incoherent Cherenkov radiation monitor status and plans

ATF2 incoherent Cherenkov radiation monitor status and plans will be presented.

Speaker: Stefano Mazzoni (CERN)

17:15 ATF2 BPMs status and plans

ATF2 BPMs status and plans will be presented.

Speaker: Alexey Lyapin (John Adams Institute at Royal Holloway, University of London)

16:00 → 17:40 Higgs, Electroweak: 4

16:00 Higgs self coupling: Theory status

Invited talk on the status of the theory of the Higgs self coupling

Speaker: Matthew Mccullough (CERN)

16:25 ECFA Study: Higgs Self-coupling

Invited talks on the ECFA Topic: Higgs self-coupling

Speaker: Sven Heinemeyer (Consejo Superior de Investigaciones Cientificas (CSIC) (ES))

16:45 New collider implications on a strongly first order EWPT.

In order to understand the early history of the universe, and to test baryogenesis models, determining the nature of the electroweak phase transition is imperative. The order and strength of this transition is strongly correlated to relatively large deviations in the $hhh$ coupling. In models where a considerable part of the $hhh$ coupling deviation is caused by charged particle loops, the $h\gamma\gamma$ coupling is also expected to deviate considerably. In this talk, by using a model-independent approach, I explain how to obtain conditions that are sufficient for a strongly first order phase transition. After the $h\gamma\gamma$ is determined with precision at the HL-LHC, these conditions can be tested at Future Linear Colliders by measurements of the $hhh$ coupling, to conclusively determine the nature of the electroweak phase transition and the viability of electroweak baryogenesis on models with new charged scalars.

Speaker: Ricardo Florentino

17:00 Double Higgs production in composite two Higgs doublet model

The precise measurement of the 125 GeV Higgs boson is one of the powerful ways to probe new physics. In particular, it is known that a large deviation from the SM predictions can appear in the di-Higgs production process e.g., via new physics effects of the triple Higgs boson coupling.
In this talk, we discuss the theoretical behavior of the di-Higgs production cross section in the composite two Higgs doublet model.
We then discuss how new particles of the model (additional Higgs bosons and heavy top quark partners) affect this process.

Speaker: Kodai Sakurai (Tohoku University)

17:15 BSM Triple Higgs couplings at the ILC/CLIC

To explain the baryon asymmetry in the universe a First Order Electroweak Phase Transition (FOEWPT) in the early universe is favored. This requires a BSM Higgs sector, which introduces additional Higgs bosons as well as the corresponding additional trilinear Higgs couplings (THCs). Taking the 2HDM as a concrete example, we discuss how such BSM THCs might be accessible at the ILC/CLIC via di-Higgs production. We also briefly analyze the effect of higher-order corrections to the THCs.

Speakers: Francisco Arco, Sven Heinemeyer (Consejo Superior de Investigaciones Cientificas (CSIC) (ES))

16:00 → 17:30 Normal conducting RF: 3

16:00 Distributed Coupling Linac for Efficient Acceleration of High Charge Electron Bunches

Future colliders will require injector linacs to accelerate large electron bunches over a wide range of energies. For example the Electron Ion Collider requires a pre-injector linac from 4 MeV up to 400 MeV over 35 m. Currently this linac is being designed with 3 m long traveling wave structures, which provide a gradient of 16 MV/m. We propose the use of a 1 m distributed coupling design as a potential alternative and future upgrade path to this design. Distributed coupling allows power to be fed into each cavity directly via a waveguide manifold, avoiding on-axis coupling. A distributed coupling structure at S-band was designed to optimize for shunt impedance and large aperture size. This design provides greater efficiency, thereby lowering the number of klystrons required to power the full linac. In addition, particle tracking analysis shows that this linac maintains lower emittance as bunch charge increases to 14 nC and wakefields become more prevalent. We present the design of this distributed coupling structure, as well as cold test data and plans for higher power tests to verify on the structure’s real world performance.

Speaker: Ankur Dhar (SLAC National Accelerator Lab)

16:20 RF breakdown studies at nanosecond timescales using structure wakefield acceleration

High-energy particle accelerators are crucial to the next big discovery in particle physics. To reduce the size and cost of particle accelerators, increasing the accelerating gradient (energy gain per unit length for the particle beam) is of critical importance. Advanced accelerator concepts (AACs) hold the promise of revolutionary future particle colliders with dramatically higher gradients than what conventional accelerator technologies allow. One advanced concept, structure wakefield acceleration (SWFA), aims to raise the gradient and the efficiency by confining the microwave energy in a short and intense pulse. The SWFA concept has inspired a new approach to generate nanosecond RF pulses with a high peak power (on the order of a few hundred megawatts). By using the short RF pulses to study RF breakdown on the nanosecond time scale, we have demonstrated that the short pulse length could potentially mitigate the impact of RF breakdown, and the beam-driven short-pulse acceleration technique could enable a new class of compact accelerators.

Speaker: Xueying Lu (Northern Illinois University / Argonne National Lab)

16:40 Summary of RF Breakdown Studies using Single Cell Standing Wave Accelerating Structures

The acceleration gradient is a critical parameter affecting the feasibility and cost of large-scale particle accelerators such as normal conducting linear colliders. The main obstacle to increasing the acceleration gradient or improving the reliability of a linear accelerator at a certain gradient is vacuum RF breakdown. To understand the basic physics of the RF breakdown in cavities suitable for use in linear colliders, we developed a setup consisting of a reusable mode launcher and a short standing wave accelerating structure. Over forty cavities have been tested over the past two decades, giving us insight into different shapes, materials and manufacturing methods. In this report we will summarize the results.

Speaker: Valery Dolgashev (SLAC National Accelerator Laboratory)

17:00 Next Generation LLRF Control Platform for Compact C band Linear Accelerator

The Low-Level RF (LLRF) control circuits of linear accelerators (LINACs) are conventionally realized with heterodyne based architectures, which have analog RF mixers for up and down conversion with discrete data converters. We have developed a new LLRF platform for C band linear accelerator based on the Frequency System-on-Chip (RFSoC) device from AMD Xilinx. The integrated data converters in RFSoC can directly sample the RF signals in C band and perform the up and down mixing digitally. The programmable logic and processors required for signal processing for LLRF control system are also included in a single RFSoC chip. With all the essential components integrated in a device, the RFSoC-based LLRF control platform can be implemented more cost-effectively and compactly, which can be applied to a broad range of accelerator applications. In this paper, the structure and configuration of the newly developed LLRF platform will be described. We have performed a detailed performance evaluation based on the requirements of C band linear accelerators and part of the characterization results will be presented and discussed.

Speaker: Chao Liu (SLAC National Accelerator Laboratory)

16:00 → 18:00 Sources: 4

16:00 Update of the CLIC positron source

The CLIC positron source was simulated and optimised. A new baseline was proposed with a single amorphous tungsten target and a flux concentrator based matching device. Misalignments of the beamline are studied. Alternative scenarios with higher positron yields are also studied.

Speaker: Mr Yongke Zhao (CERN)

16:20 Hydrodynamic Simulations of an Argon-filled Tapered Plasma Lens for Optical Matching at the ILC $e^+$ Source

The beam produced in the target of the ILC positron source is highly divergent and therefore requires immediate optical matching, conventionally performed by some kind of solenoid arrangement.
Recently, the use of a plasma lens has been considered as an alternative with hopes to increase number of positrons available for the downstream acceleration. Previous simulations have indicated that a plasma lens design with linear tapering is optimal for the ILC positron source.
In the latest hydrodynamic simulations, argon is studied as the plasma medium for the aforementioned plasma lens design. During these studies, argon’s various reaction paths are systematically examined to understand their impact on the discharge process. This is followed by a comparison with hydrogen.

Speaker: Manuel Formela (Universität Hamburg/DESY)

16:40 Update on plasma stability measurements of the prototype plasma lens for positron matching

The quest for novel technologies in the ever-evolving landscape of scientific exploration has led to the investigation of plasma lensing as a potential solution for optical matching devices at positron sources. This research becomes increasingly significant as the need for higher data output demands innovative concepts to increase positron yield and therefore luminosity. Our initial experiments revealed instabilities within the gas discharge. This talk will focus on the analysis of high temporal resolution measurements and the operation state of the prototype lens. Understanding and overcoming these challenges is pivotal for a future application of plasma lenses as an integral part of high performance positron sources.

Speaker: Niclas Hamann (Uni Hamburg/DESY Hamburg)

17:00 Update for undulator-based positron sources for ILC and HALHF

The undulator-based positron source is baseline design for the ILC. Recent progress in particular on the undulator masc designs, optic matching devices (R&D for prototypes for pulsed solenoid, plasma lens) and on the target design (rotating wheel, material tests) are discussed. The adaption of an undulator-based positron source for the HALHF design as an upgrade option for the ILC is included as well.

Speaker: gudrid moortgat-pick

17:20 Mechanical design studies of the pulsed solenoid for positron sources

We give a status report of prototyping a pulsed solenoid as an optic matching device for the undulator-based positron source of the ILC. In light of studies [1] and [2], we explore various design possibilities for the pulse solenoid coil. It is proposed to rotate the coil turns at an angle equal to the flare angle of the solenoid cone, which should improve the magnetic "looseness" of the coil [3] and reduce the dissipation of magnetic flux through the inter-turn spiral gap.
Additionally, two alternative methods for securing the solenoid turns are considered. The first involves independently fixing each adjacent turn to the next, rather than using a single element to secure all turns simultaneously. The second method employs an external ceramic shell to hold the turns in place.
[1] R&D for Positron Sources at High-Energy Lepton Colliders \ Gudrid Moortgat-Pick, Sabine Riemann, Peter Sievers, Carmen Tenholt
[2] Mechanical and thermal stress on a pulsed solenoid for positron capture at the ILC undulator-based positron source \ C. Tenholt, G. Loisch, M. Mentink, M. Fukuda, G. Moortgat-Pick, T. Okugi, S. Riemann, P. Sievers, K. Yokoya \ LCWS2023, SLAC, US.
[3] Some problems of high field pulsed magnets development. \ R. Lapik, P. Martyshkin, A. Yakutin

Speaker: Dr Grigory Yakopov (DESY)

16:00 → 17:30 Superconducting RF: 6

Convener: Marc Wenskat (DESY)

16:00 Supercondtucting Thin Films on Higher Order Mode Antennas to Increase the CW Performance of SRF Cavities at MESA

The Mainz Energy-recovering Superconducting Accelerator (MESA), an energy-recovering (ER) LINAC, is currently under construction at the Institute for Nuclear physics at the Johannes Gutenberg-Universität Mainz, Germany. In the ER operation mode, continuous wave (CW) beam is accelerated from 5 MeV up to 105 MeV. The energy gain of the beam is provided through 2 enhanced ELBE-type cryomodules containing two 1.3 GHz 9-cell TESLA cavities each. By pushing the limits of the beam current up to 10 mA, a quench can occur at the higher order modes (HOM) antennas. The quench is caused by the increased power deposition induced by the electron beam in ER mode. Calculations have shown that an upgrade from 1 mA to 10 mA can increase the deposited power in the HOMs up to 3080 mW. From this power approximately 30% will be present at the HOM feedthrough and can be used as a thermal input. Previous simulations have shown a power limit of 95 mW, which includes the power of a recirculating beam at 1 mA but is exceeded at 10 mA. A solution to increase the power limit is to coat the antennas with a superconducting thin films which provides higher critical fields, temperature, and currents. Nb_3 Sn and NbTiN are the material candidates . First simulations shown an increased power limit, which includes the limits for MESA.

Speaker: Paul Plattner (JGU Mainz)

16:20 High-Q cavities measurements and diagnostics

Research and development on high-Q cavities requires extensive experimental campaigns to understand the origin of possible performance limitations and then to study the effect of more advanced surface treatments on the physical mechanisms governing such a high-Q operating regime.
From the experimental point of view, significant effort must be made to avoid flux trapping, either by canceling the remanent field or by rapid cooling procedures. To this end, INFN LASA has initiated an upgrade of its vertical test facility. Ongoing activities include the construction of a new dedicated cryostat, the development of an experimental system for external magnetic flux control and regulation, and the integration of a wide range of diagnostics for quench and field emission events. As examples, some experimental results on prototype high-Q cavities are reported and discussed.

Speaker: MIchele Bertucci (INFN sezione di Milano)

16:40 Nb3Sn on Cu thin film SRF cavities for new generation LINACS operating at 4.5 K

Energy saving is mandatory for new generation linacs and accelerators more generally. Cryogenics is one of the major energy costs in modern SRF accelerators because of the need to lower the operating temperature to 2K. Substituting Nb with a higher critical-temperature superconductor, such as Nb3Sn, allows operations to be moved up to 4.5 K with a reduction in cryogenic costs by a factor of 3. On I.FAST collaboration R&D activity cover all the cavity production chain with the goal of producing the first prototype of a Nb3Sn on Cu 1.3 GHz elliptical cavity. This work will show the results obtained at INFN LNL with Plasma Electrolytic Polishing for substrate preparation and the solutions adopted to optimize Nb3Sn coatings via DCMS. First RF measurements on planar quadrupole resonator will also be shown and finally the scalability from small flat samples to elliptical cavity prototype will be also discussed in the conclusions.

Speaker: Cristian Pira (INFN LNL)

17:00 Strategy for cavity R&D towards an upgrade of the European XFEL - current performance and the need for a new specification

Based on the success of the European XFEL srf cavity production, several projects worldwide (LCLS-2, SHINE, etc.) applied and further developed the underlying technology, specifically for cw application with higher Q-value and moderate operation gradients up to 21 MV/m. For a high-duty cycle (hcd) / cw upgrade of the European XFEL, it is required to preserve the high gradient operation in the original pulsed mode aiming for gradients > 25 MV/m in addition to the need for high Q-values (~3e10) at moderate gradients in hdc mode.
In the last years the focus at DESY to achieve this requirements is on the "Mid-T treatment" significantly simplifying the surface preparation process. A summary of results on single-cell cavities will be presented.
In parallel, 15 years after the European XFEL specification for the cavity series production, DESY identified its demand to adapt the specification to the actual state-of-the-art in srf technology, but to keep the mandatory fundamentals including a consolidated contractor supervision. The order of 10 new XFEL-type nine-cell cavities will allow to handover the know-how and a gain of experience to a (partially) new generation of experts. In an extensive test phase the results of the Mid-T treatment R&D will be transferred to the cavities before they will be used to refurbish the low-performing XFEL accelerator module XM99.

Speaker: Detlef Reschke (DESY)

16:10 → 17:30 BSM, Global Interpretations: 5

16:10 Probing GHU models at the ILC with di-quark AFB at c.m.e. above the Z mass

We discuss the experimental prospects for measuring differential observables in b-quark and c-quark pair production at the International Linear Collider (ILC) baseline energies, 250 and 500 GeV. The study is based on full simulation and reconstruction of the International Large Detector (ILD) concept. Two gauge-Higgs unification models predicting new high-mass resonances beyond the Standard Model are discussed. These models predict sizable deviations of the forward-backward observables at the ILC running above the mass and with longitudinally polarized electron and positron beams. The capability of the ILC to probe these models via high-precision measurements of the forward-backward asymmetry is discussed.
Alternative scenarios at other energies and beam polarization schemes are also discussed, extrapolating the estimated uncertainties from the two baseline scenarios.

Speaker: Adrian Irles (IFIC (CSIC/UV) Valencia)

16:30 Global EFT fits for future colliders

We present SMEFiT3.0, an updated global SMEFT analysis of Higgs, top quark, and diboson production data from the LHC complemented by electroweak precision observables (EWPOs) from LEP and SLD. We consider recent inclusive and differential measurements from the LHC Run II and estimate the impact of HL-LHC measurements on the SMEFT parameter space when added on top of SMEFiT3.0, through dedicated projections extrapolating from Run II data. We quantify the significant constraints that measurements from two proposed high-energy circular colliders, the FCC-ee and the CEPC, would impose on both the SMEFT parameter space and on representative UV-complete models. The framework presented in this work may be extended to other future colliders and running scenarios, providing timely input to ongoing studies towards future high-energy particle physics facilities.

Speaker: Eleni Vryonidou (University of Manchester (GB))

16:55 CP-violating top-Higgs coupling in SMEFT

The total cross section of the process $\mu^-\mu^+\to\nu_\mu\bar{\nu}_\mu t\bar{t}H$ has strong dependence on the CP phase of the top Yukawa coupling. We study the cause of the strong energy dependence and identify its origin as the $E/m_W$ growth of the weak boson fusion subamplitudes, $W^-W^+\to t\bar{t}H$, when the two $W$’s are longitudinally polarized. We repeat the study in the SMEFT framework where EW gauge invariance is manifest and find that the highest energy cross section is reduced to a quarter of the complex top Yukawa model result at high energies. By applying the Goldstone boson (GB) equivalence theorem, we identify the origin of this strong energy growth of the SMEFT amplitudes as associated with the dimension-6 $ttH\pi\pi$ vertex, where $\pi$’s are the GB of $W^\pm$. We obtain the unitarity bound on the coefficient of the SMEFT operator by studying all $2\to2$ and $2\to 3$ cross sections in the $J = 0$ channel.

Speaker: Ya-Juan Zheng

17:15 Probing SMEFT operators using polarizations and spin correlations at current and future colliders

The standard Model (SM) is the best currently experimentally tested theory of fundamental particles and their interactions. The discovery of Higgs boson completes the particle spectrum of SM and now the particle physics have officially entered the era of precision measurement. While the SM enjoys robust experimental verification, it falls short in explaining phenomena like the naturalness problem, dark matter, strong CP problem, matter-antimatter asymmetry, and neutrino mass. Various beyond SM models, including supersymmetry, Technicolor, UED, and string theory, have been proposed to address these issues, yet experimental evidence for new particles, symmetries, or dimensions remains elusive.

In response to the null results from the experiments, a shift toward a model-independent formalism becomes imperative. The effective field theory (EFT) serves as a versatile framework, expanding the SM by introducing higher-order gauge symmetric Lorentz terms. While the gauge symmetry imposes constraints on deviations in the fermionic sector, the likelihood of significant deviations in this sector is notably reduced. However, the electroweak sector remains open to exploration. We study the potential of future electron-positron colliders, particularly the International Linear Collider (ILC), to probe higher-order operators affecting the electroweak gauge sector. The study is carried with polarized beams which aid on increasing the signal-to-background ratio.\

To maximize sensitivity to new physics signals, a diverse set of observables is crucial. Here, we delve into the significance of spin-related observables, offering numerous polarization and spin correlation options. These set of observables could also shed light on the CP structure and correlations of new physics. One has to note that the construction of vector polarization and their correlations with the tensorial polarizations demands the proper identification of final daughter of weak bosons. The tagging of daughters becomes non-trivial in case of light flavor jets and to overcome these challenges, we propose employing machine learning techniques such as artificial neural networks, boosted decision trees, and convolutional neural networks. We show for the hadronic decay of $W$ boson an accuracy of $80\%$ can be achieved. The $95\%$ CL bounds on anomalous couplings is found to be tighter than the experimental values. Finally we note that besides playing a dominant role on probing higher order operators, spin-related observables can be directly used to comment on the existence of quantum entanglement at high energy.

Speaker: Amir Subba (Indian Institute of Science Education and Research, Kolkata)

19:30 → 21:30 Banquet

Thursday, 11 July

09:00 → 10:30 Early Career Researcher: ECR forum

Conveners: Ruth Magdalena Jacobs (Deutsches Elektronen-Synchrotron (DE)), Shion Chen (Kyoto University (JP))

09:00 Prospect talk - Physics

Speaker: Tomohiro Abe

09:15 Prospect talk - Accelerator

Speaker: Spencer Gessner (SLAC)

09:30 Prospect talk - Detector

Speaker: Yuji Enari (High Energy Accelerator Research Organization (JP))

09:45 Summary of the ECR survey

A summary on the survey done in the ECR communities ahead of the conference.

Speakers: Dimitris Ntounis (SLAC National Accelerator Laboratory (US)), Emanuela Musumeci (Univ. of Valencia and CSIC (ES)), Ruth Magdalena Jacobs (Deutsches Elektronen-Synchrotron (DE)), Yuki Abe (SOKENDAI(KEK)), Leonhard Reichenbach (CERN / University of Bonn (DE)), Samuel Homiller, Yasuhito Sakaki (KEK), Shion Chen (Kyoto University (JP))

10:00 Q&A panel discussion

A panel discussion on the questions/agenda based on the ECR survey.

Speakers: Adrian Irles (IFIC (CSIC/UV) Valencia), Hitoshi Murayama (University of California Berkeley (US)), Jenny List (Deutsches Elektronen-Synchrotron (DE)), Dr yoshinori enomoto (KEK)

10:30 → 11:00 coffee

11:00 → 12:30 Accelerator Plenary: working group summaries

Convener: Emilio Nanni (SLAC National Accelerator Laboratory)

11:00 Sources

11:10 Damping rings, Beam delivery systems

Speaker: Andrea Latina (CERN)

11:20 Beam dynamics

11:30 Superconducting RF

Speaker: Yasuchika Yamamoto (KEK)

11:40 Normal conducting RF

11:50 Advanced Accelerator Concepts

12:00 Applications

12:10 Conventional Facilities, Machine Detector interface

11:00 → 12:30 Physics & Detector plenary: working group summaries

11:00 Higgs, Electroweak

11:15 Top, QCD, Flavor, Precision Modelling

11:30 BSM, Global Interpretations

11:45 Vertex, Tracking, Timing detectors

12:00 Calorimetry, Muon detectors

12:15 Software, Reconstruction, Computing

12:30 → 14:00 Lunch

14:00 → 15:30 Plenary: Closing 1

Convener: Geoffrey Norman Taylor (University of Melbourne (AU))

14:00 Communication

Speaker: Rika Takahashi (KEK)

14:15 Strategy in Japan

Speaker: Tsuyoshi Nakaya (Kyoyo U.)

14:30 Perspectives from the US for a Higgs Factory

Speaker: Abid Patwa (U.S. Department of Energy)

14:45 European Strategy (remote talk)

Speaker: Karl Jakobs (Albert Ludwigs Universitaet Freiburg (DE))

15:00 Global Strategy - ICFA view (remote talk)

Speaker: Pierluigi Campana (INFN e Laboratori Nazionali di Frascati (IT))

15:15 Poster awards

15:30 → 16:00 coffee

16:00 → 17:45 Plenary: Closing 2

16:00 New Technologies for Higgs Factory Detectors

Speaker: Marcel Demarteau (Oak Ridge National Laboratory)

16:25 Physics Vision

Speaker: Hitoshi Murayama (University of California Berkeley (US))

16:50 Vision for a Linear Collider Facility

Speakers: Jenny List (Deutsches Elektronen-Synchrotron (DE)), Steinar Stapnes (CERN)

17:15 The way forward

Speaker: Tatsuya Nakada (EPFL - Ecole Polytechnique Federale Lausanne (CH))

17:30 Closing