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.

 

LCWS2024_poster.pdf

Monday, 8 July

08:30 Registration

Plenary: Opening 1

1 Opening remarks

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

2 Physics case for Higgs and Electroweak precision

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

3 ILC status

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

4 CLIC status

Speaker: Steinar Stapnes (CERN)

5 Status of the C3 R&D

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

6 Physics case for e+e- at 500 GeV and above

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

10:30 coffee

Plenary: Opening 2

7 HALHF status

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

8 XCC status

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

9 Energy recovery at a Linear Collider

Speaker: Vladimir Litvinenko

10 CEPC status

Speaker: Jie Gao (IHEP)

11 FCCee status

Speaker: Michael Benedict (CERN)

12 Muon collider status

Speaker: Daniel Schulte (CERN)

13 Higgs Factory detector R&D

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

12:40 Lunch

Accelerator Plenary

14 ITN: accelerator developments

Speaker: Shinichiro Michizono (KEK)

15 CLIC: accelerator developments

Speaker: Philip Burrows

16 C3: accelerator developments

Speaker: Ankur Dhar (SLAC National Accelerator Lab)

17 CEPC: accelerator developments

Speaker: yuhui li

18 FCCee: accelerator developments

Speaker: Frank Zimmermann (CERN)

19 Energy Upgrades of a linear Higgs factory

Speaker: Emilio Nanni (SLAC National Accelerator Laboratory)

Physics & Detector plenary

20 ECFA Higgs-EW-top factory study

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

21 Physics highlight 1, experimental challenges

22 Physics highlight 2, experimental challenges

23 Beyond collider experiments at a Linear Collider

Speaker: Yasuhito Sakaki (KEK)

24 Highlights from LHC detector upgrades

Speaker: Gustaaf Brooijmans (Columbia University)

25 Highlights from detectors for EIC

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

15:30 coffee

Plenary: Discussion - Global Vision for a Linear Collider facility

Poster: poster session

26 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)

27 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

28 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

29 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)

30 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

31 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)

32 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)

33 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)

34 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)

35 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 Reception & Poster session

Tuesday, 9 July

Advanced Accelerator Concepts: 1

BSM, Global Interpretations: 1

36 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)

Calorimetry, Muon detectors: 1

Damping rings, Beam delivery systems: 1

Higgs, Electroweak: 1

Sources: 1

Superconducting RF: 1

10:30 coffee

Conventional Facilities, Machine Detector interface: 1

Damping rings, Beam delivery systems: 2

Higgs, Electroweak: joint with BSM/GI

Normal conducting RF: 1

Superconducting RF: 2

Top, QCD, Flavor, Precision Modelling: 1

Vertex, Tracking, Timing detectors: 1

12:30 Lunch

BSM, Global Interpretations: 2

Industry: Sustainability

Software, Reconstruction, Computing: 1

Top, QCD, Flavor, Precision Modelling: 2

15:30 coffee

Industry: Sustainability

Wednesday, 10 July

BSM, Global Interpretations: 3

Beam Dynamics: 1

Calorimetry, Muon detectors: 2

Higgs, Electroweak: 2

Sources: 2

Superconducting RF: 3

Vertex, Tracking, Timing detectors: 2

10:30 coffee

BSM, Global Interpretations: 4

Conventional Facilities, Machine Detector interface: 2

Higgs, Electroweak: 3

Normal conducting RF: 2

Software, Reconstruction, Computing: 2

Sources: 3

Superconducting RF: 4

12:30 Lunch

Advanced Accelerator Concepts: 2

Applications: 1

BSM, Global Interpretations: joint with HiggsEW

Beam Dynamics: 2

Software, Reconstruction, Computing: 3

Superconducting RF: 5

Top, QCD, Flavor, Precision Modelling: 3

EAJADE: by invitation

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

15:30 coffee

Applications: 2

BSM, Global Interpretations: 5

Calorimetry, Muon detectors: 3

Conventional Facilities, Machine Detector interface: 3

Higgs, Electroweak: 4

Normal conducting RF: 3

Sources: 4

Superconducting RF: 6

19:30 Banquet

Thursday, 11 July

Plenary: Early Career Researcher forum

10:30 coffee

Accelerator Plenary: working group summaries

Physics & Detector plenary: working group summaries

12:30 Lunch

Plenary: Closing 1

37 Communication

Speaker: Rika Takahashi (KEK)

38 Strategy in Europe

39 Strategy in the US (tbc)

Speaker: Abid Patwa (DOE)

40 Strategy in Japan

Speaker: Tsuyoshi Nakaya (Kyoyo U.)

41 Global Strategy - ICFA view

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

15:30 coffee

Plenary: Closing 2

42 New Technologies for Higgs Factory Detectors

Speaker: Marcel Demarteau (Oak Ridge National Laboratory)

43 Physics Vision

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

44 Vision for a Linear Collider Facility

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

45 Poster awards

46 Closing