International Workshop on Future Linear Colliders 2026

9 Nov 2026, 08:00 → 13 Nov 2026, 18:00 Asia/Tokyo

KEK

The International Workshop on Future Linear Colliders 2026 (LCWS2026) continues the established series devoted to the study of the physics, detectors, and accelerator technologies for high-energy electron–positron colliders.

Linear colliders are one of the most compelling options for a next-generation Higgs factory, complementary to circular collider proposals. They offer a unique and flexible path toward higher centre-of-mass energies and luminosities, enabling a long-term exploration of the electroweak scale and beyond. At the same time, many key technologies and physics goals are shared across linear and circular approaches, opening important opportunities for synergy and collaboration within the global community.

Since the last workshop (LCWS2025), significant progress has been made in both linear collider concepts and the broader Higgs factory landscape. LCWS2026 will highlight recent developments and future prospects, with particular emphasis on the long-term vision of linear colliders—including energy and luminosity upgrades—as well as their interplay with circular collider initiatives.

With a comprehensive program of plenary and parallel sessions, the workshop will provide an opportunity to present ongoing work, exchange ideas, and foster collaboration across communities working toward future Higgs factories.

The workshop is scheduled from 9th to 13th of November at KEK. More detailed information will follow.

 

Sponsors

 

 

 

 

 

 

 

LCWS2026_A2_web.pdf

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Visa Support Request Form_LCWS2026.xlsx

Monday 9 November

09:30 → 10:30 Registration

10:30 → 12:40 Plenary: Plenary Mon-1

10:30 Welcome

Speakers: Hiroshi Sakai (KEK), Hiroshi Sakai (Institute for Solid State Physics, University of Tokyo)

10:35 LOC

Speaker: Takeshi Dohmae

10:45 KEK's activity

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

11:05 The linear collider study at CERN

Speaker: Alessandra Lombardi (CERN)

11:25 Status of LEP3

Speaker: Edda Gschwendtner (CERN)

11:45 Status of FCC-ee

Speaker: Michael Benedikt (CERN)

12:05 Status of CEPC

Speakers: Jie Gao (IHEP), Jie Gao (Chinese Academy of Sciences (CN))

12:15 ILC-Japan

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

12:25 US perspective

Speaker: Cameron Geddes (LBNL)

12:40 → 13:45 Lunch

13:45 → 14:00 Group photo

14:00 → 15:40 Plenary: Plenary Mon-2

14:00 IDT status

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

14:10 View from ICFA

Speaker: Tsuyoshi Nakaya (Kyoto University)

14:30 Physics overview (title TBD)

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

15:10 A Linear Collider approach to answer the big question

Speaker: Roman Poeschl (Université Paris-Saclay (FR))

15:40 → 16:15 Coffee break

16:15 → 17:45 Plenary: Plenary Mon-3

16:15 Upgrade paths: advanced high-gradient RF techniques (C^3) and ERL

Speaker: Emilio Nanni

16:45 Upgrade paths: plasma wakefield opportunities

Speaker: Marlene Turner (CERN)

17:15 General discussion - upgrade options

Speakers: Emilio Nanni, Marlene Turner (CERN)

18:00 → 20:00 Reception: Reception/Poster session

Tuesday 10 November

09:00 → 10:30 Plenary: Plenary Tue-1

09:00 ILD status, including an overview of LC detector status (status for all, incl. HALHF)

Speaker: Junping Tian (University of Tokyo)

09:30 Recent highlights on vertexing/tracking/timing

Speaker: Peter Kluit (Nikhef National institute for subatomic physics (NL))

09:50 Recent highlights on calorimetry/PID

Speaker: Prof. Wataru Ootani (ICEPP, Univ. of Tokyo)

10:10 Software development (including key4hep)

Speakers: Frank Gaede, Frank-Dieter Gaede (Deutsches Elektronen-Synchrotron (DE))

10:30 → 11:00 Coffee break

11:00 → 12:30 Plenary: Plenary Tue-2

11:00 ITN (ILC Technology Network)

Speaker: Shinichiro Michizono (KEK)

11:30 LCF@CERN: update on RTML and Main Linac studies

Speaker: Andrea Latina (CERN)

11:50 LCF@CERN: update on BDS/MDI/x-angle studies

Speaker: Rogelio Tomas Garcia (CERN)

12:10 LCF@CERN: update on Conventional Facilities and Siting studies

Speaker: Edward Fraser MacTavish (CERN)

12:30 → 14:00 Lunch

14:00 → 15:30 Beam dynamics; beam delivery systems, main linacs, damping rings

14:00 → 15:30 Beyond Colliders Opportunities

14:00 CERN’s Non-Collider Physics Roadmap

CERN’s scientific program extends well beyond its flagship collider experiments, thanks to early considered flexibility and strategic choices when its diverse and flexible injector chain and accelerator infrastructure were and are conceived. This allows for a broad ecosystem of fixed-target, antimatter, rare-isotope, neutron, neutrino and forward-physics activities, exploited through the Laboratory’s accelerator complex, experimental areas and shared technical infrastructure. Building on these capabilities, following the successful Physics-Beyond-Collider initiative (PBC), CERN has launched the Non-Collider Physics Roadmap (NCPR), covering the period 2027–2046, to establish a coherent long-term framework for the evolution of this diverse program alongside the High-Luminosity LHC and future major accelerator projects.

After a short recap of PBC objectives and results, this presentation will introduce the motivation, scope and process of the NCPR and illustrate how CERN currently prepares and analyses roadmap options and pathways. It will highlight how beams, experimental areas and common infrastructure can support complementary scientific programs over the years to come, provided that their requirements, constraints and opportunities are identified sufficiently early. In line with CERN’s long-term plan, a selection of possible future projects, combined with upgrade and required consolidation activities, will illustrate some of the presently considered roadmap pathways.

Beyond the immediate CERN roadmap, the NCPR may provide an opportunity to further discuss how a diverse scientific ecosystem can be considered collectively. Future opportunities can be assessed in terms of scientific complementarity, maturity, infrastructure requirements, resources, timelines and uniqueness within a given laboratory and the worldwide landscape. Fitting to this conference scope, a future major accelerator facility should therefore be conceived from the outset not solely as an e⁺e⁻ collider, but as a versatile scientific infrastructure capable of supporting a broad and evolving long-term research program.

Speaker: Markus Brugger (CERN)

14:25 Beam Parameters, Layout and Opportunities for Beyond-Collider Experiments at a Linear Collider Facility

Speaker: Benno List (DESY)

14:45 CERN’s present and future test-beam capabilities

Test beams are essential for developing and validating detector technologies for future colliders. The CERN PS East Area and SPS North Area provide complementary beams of electrons, muons and hadrons, including pions, kaons and protons. The East Area covers the low-momentum range, extending from sub-GeV/c momenta up to 15 GeV/c, while the North Area provides secondary beams up to 360 GeV/c and attenuated primary proton beams at 400 GeV/c. Ion beams are also available in selected beamlines. Adjustable beam intensities, momentum selection and dedicated instrumentation for beam characterisation and particle identification support tests ranging from individual sensors to large detector prototypes. This contribution will review these capabilities and the available experimental infrastructure, with particular attention to detector R&D for future electron–positron colliders. It will present recent improvements, including developments towards lower-momentum beams and high-quality electron beams, discuss planned infrastructure upgrades and provide an outlook on future beam availability.

Speaker: Johannes Bernhard (CERN)

15:05 Crystal-Based Technologies for Electron–Positron Colliders

Crystals can channel charged particle beams along major crystallographic directions, providing a compact and efficient tool for beam manipulation at high energies. In bent crystals, channeled particles follow the crystal curvature, enabling beam steering over very short distances. While this technique has been extensively investigated for hadron beam collimation and extraction at the CERN SPS and LHC, as well as at FNAL, its application to electron and positron beams is attracting increasing interest in view of future high-energy lepton accelerators.

For future linear colliders, crystal-based technologies may contribute to several key areas, including beam extraction and manipulation, intense photon generation, and positron production. In oriented crystals, coherent interactions can strongly enhance electromagnetic radiation compared with ordinary bremsstrahlung, enabling compact sources of high-energy photons. Crystalline undulators further extend this concept, offering the possibility of generating hard X-rays and gamma rays at sub-ångström wavelengths through the periodic motion of channeled particles.

A particularly promising application is the use of oriented crystals as photon radiators for high-intensity positron sources, a concept originally proposed by Chehab and Variola and later developed by Chehab, Chaikovska and collaborators for CLIC, with important experimental tests carried out at KEK. The enhanced radiation emission can improve positron production while reducing the energy deposition in the conversion target.

This contribution reviews recent experimental and technological advances in crystal-based beam manipulation and radiation generation, with particular emphasis on their potential applications to future electron–positron linear colliders.

Speaker: Laura Bandiera (Universita e INFN, Ferrara (IT))

14:00 → 15:30 Conventional Systems and MDI

14:00 The Civil Engineering for a Future Linear Collider at CERN

The Civil Engineering design of a future Linear Collider at CERN requires the integration of accelerator requirements, site constraints, underground infrastructure and long-term upgrade strategies. As part of the Phase 1 preparation plan (2026–2028), implementation studies are being undertaken for both the CLIC and LCF configurations, addressing siting, civil engineering and conventional infrastructure.
The studies investigate two alternative future linear colliders which could serve in the post LHC era. CLIC is proposed as a staged development, initially constructing a 12.1 km tunnel for a 380 GeV machine before extending to 29.6 km for 1.5 TeV. In contrast, the LCF proposes construction of the full 33.5 km tunnel system in a single stage, providing the infrastructure required for its initial 250 GeV configuration and subsequent 550 GeV upgrade. Although the two designs share major civil-engineering components, differences in injection infrastructure, underground services and machine length lead to distinct construction and land use requirements.
A major focus of the ongoing work is the optimisation of the collider layout and placement. Tunnel alignments are being assessed using a sensitivity grid, building on methodology developed for the FCC studies. The analysis considers geological suitability, with particular emphasis on maintaining construction within favourable Molasse rock, alongside land availability and surface constraints.
Another focus is placed on the Interaction Region and Beam Delivery System, following the evolution to a two-detector configuration. Two civil engineering solutions are being assessed: a single large cavern accommodating both detectors, and two separated detector caverns served by independent beamlines and dedicated civil infrastructure. These options present different trade-offs between detector accessibility, radiation shielding as well as structural and magnet stability.
The ongoing studies aim to establish an optimised civil engineering solution for a future Linear Collider at CERN, balancing geological, technical, environmental and construction constraints while maintaining flexibility for future energy upgrades and scientific diversification.

Speaker: Edward Fraser MacTavish (CERN)

14:20 Recent study on the main beam dump

Report on the alternative design for achieving vortex water flow.
This includes simulation results and an update on progress with preparing a small-scale test module.

Speaker: Dr Nobuhiro Terunuma (KEK)

14:40 Precision Luminometry updates for ILC, FCC-ee

We present updates to previous years work on luminometry at ILC and FCC-ee at various scenarios, from Z pole to ZH threshold and to ttbar threshold.

Speaker: Brendon Madison (University of Kansas)

15:00 Adapting the ILD Detector for HALHF

HALHF is a proposed linear e+e- collider, which uses the novel acceleration technology of PWFA to create high-energy collisions necessary for a Higgs factory. The highly asymmetric nature of the collisions at HALHF calls for an asymmetric detector to effectively capture the signal while avoiding background. In this work, the traditionally symmetric ILD detector, originally designed for colliders upto 1TeV center-of-mass energy, is modified to enhance forward coverage and mitigate beam-induced backgrounds, such as incoherent pair productions and Compton scattering. We present the impact of these backgrounds on the detector design and compare the performance of Higgs physics analyses at HALHF to other proposed colliders such as ILC.

Speaker: Shriyansh Ranjan (DESY)

14:00 → 15:30 Joint: Higgs/EW and BSM

14:00 Probing the Real Triplet Higgs Model with Higgsstrahlung at future electron-positron colliders

Future $e^+e^-$ colliders will measure the Higgsstrahlung cross section $e^+e^- \to Zh$ with sub-percent precision, offering a unique window into probing extended scalar sectors. We present a complete one-loop electroweak calculation of this process in the real triplet Higgs model with a non-zero triplet vev, using a fully automated renormalisation procedure in the on-shell scheme. All counterterms, including those for the mixing angle between the real triplet and the doublet scalars and tadpoles in the PRTS scheme, are derived systematically, and the cancellation of UV and IR divergences is verified numerically with the help of FeynCalc and FormCalc. By constructing the ratio of the NLO BSM cross section to the SM prediction, we derive sensitivity contours in the plane of the triplet mass and scalar potential parameters, corresponding to the projected experimental precision. We further confront the model with the recent LHC hints for a $\sim 152$\,GeV di-photon resonance, which can be explained by the neutral component of the triplet. Our results demonstrate that precision Higgsstrahlung measurements at future lepton colliders provide complementary sensitivity to direct searches and can test the parameter regions favored by the LHC anomalies.

Speaker: Mohamed Younes SASSI (Tsung-Dao Lee Institute, Shanghai Jiao Tong University)

14:18 On the Phenomenology of the Real Inert Singlet-Triplet Dark Matter Model at current and future colliders

I will present a comprehensive phenomenological study of the real inert singlet-triplet dark matter model. This model extends the Standard Model (SM) with 2 inert scalars: a gauge-singlet and an SU(2)_L-triplet with hypercharge 0. The analysis takes into account state-of-the-art theoretical and experimental constraints. A central focus of our work lies on beyond-the-SM (BSM) two-loop corrections to key Higgs observables, mainly the trilinear Higgs self-coupling and the Higgs-to-diphoton partial decay width. For these, the leading two-loop contributions arising from the extended scalar sector have been computed. The impact on di-Higgs production processes at present and future colliders is explored. Finally, I will compare this model with the well-studied Inert Doublet Model (IDM) and Inert Triplet Model (ITM), highlighting unique signatures of the singlet-triplet model.

Speaker: Dr Johannes Braathen (DESY)

14:36 Model distinction at e+e- colliders: N2HDM vs. 2HDMS

We analyze two models, the 2HDM extended by a real singlet, N2HDM, and by a complex singlet (2HDMS) for the parameter space that yields a good description of the 95 GeV excesses observed by CMS, ATLAS and LEP. We demonstrate that the differences between the two models are manifest in the triple Higgs couplings. Precision measurements of various di-Higgs production channels can yield a model distinction, even if the mass spectra and other particle couplings are (nearly) identical between the two models. This constitutes a general idea how BSM Higgs sectors can be distinguished at future e+e- colliders.

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

14:54 UV completion of extended Higgs sectors from dynamics of SU(2) gauge theory

Extended Higgs sectors are motivated by various problems beyond the Standard Model, such as dark matter, neutrino masses, and the baryon asymmetry of the Universe.
Future linear colliders provide powerful probes of such scenarios through precision measurements of Higgs properties, including the Higgs self-coupling.
In many extended Higgs models, scalar quartic couplings tend to grow toward higher energies due to their positive beta functions, potentially developing a Landau pole below the Planck scale and thereby requiring a UV completion.
In this talk, we discuss possible ultraviolet completions of extended Higgs sectors motivated by various BSM problems.
We consider a confining SU(2) gauge theory as an ultraviolet completion and classify the symmetries in the theory to investigate what types of extended Higgs sectors can emerge in the infrared.
We show that a broad class of phenomenologically motivated extended Higgs sectors can be realized within this common ultraviolet framework.
This talk is based on Phys.Rev.D 113 (2026) 5, 055020.
(Notice: As I write in the comment, I can give a talk with the schedule on Nov. 10.)

Speaker: Yushi MURA (KEK)

15:12 A composite Higgs model of first order EW phase transition and its collider signatures

After the Higgs boson discovery, electroweak phase transition (EWPT) became a frontier of high-energy physics and cosmology. While EWPT is a crossover in the Standard Model, some of the promising BSM scenarios, like electroweak baryogenesis, require that it be strongly first-order. Extended Higgs models make it possible to realize such a strongly first-order EWPT. What is the fundamental model of the extended Higgs models? One of the interesting candidates is the composite Higgs model, in which Higgs bosons are pseudo-Nambu-Goldstone bosons of spontaneous breaking of global symmetries at high energies. However, it is not easy to realize strongly first-order EWPT in the Higgs sectors predicted in the composite Higgs models as it is. We here present a new scenario of strongly first-order EWPT in the $SO(6)/SO(5)$ composite Higgs model introducing explicit breaking terms of the symmetries. The low-energy effective field theory is a specific singlet extension of the Higgs sector, whose parameter space is constrained by the theoretical bounds via matching conditions and also by the low-energy experimental data. This scenario gives a strong prediction on the Higgs boson couplings. We discuss the collider signatures at future linear colliders, such as Higgs boson decays and also di-Higgs production.

This work is based on a collaboration with Shinya Kanemura, Yushi Mura, and Tetsuo Shindou, and the paper is in preparation.

Speaker: Yunita Kristanti Andriani (The University of Osaka)

14:00 → 15:30 Superconducting RF Systems

14:00 The recent progress of ITN project at KEK

Within the framework of the MEXT-ATD program and the ILC Technology Network (ITN), an ILC prototype cryomodule is currently under design and construction at KEK. It will incorporate eight superconducting 9-cell 1.3 GHz TESLA cavities. In parallel, the infrastructure required for cryomodule testing and operation is also being established. In this contribution, we report on the current status of the cryomodule components, including the superconducting radio-frequency cavities, fundamental power couplers, cavity frequency tuners, cavity magnetic shielding, superconducting quadrupole magnet, and the cryomodule vacuum vessel. In addition, the status of external systems and infrastructure is presented, covering the refrigeration plant, the high-power and low-level RF systems, the bunker, and the clean-room equipment for cryostring assembly.

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

14:20 Recent progress of the ITN cryomodule production and preparation of COI facility at KEK

Speaker: Dr Takafumi Hara (KEK)

14:40 Automated SRF Cavity Vertical Testing Using MicroTCA.4-Based Digital LLRF System

The vertical test (VT) stand at the KEK Superconducting RF Testing Facility (STF) currently uses an analog RF control system. We are in the process of replacing this system with a new digital LLRF system based on the MicroTCA.4 architecture. The digital system also allows for greater flexibility regarding configurability and software automation. It is our goal to automate the VT process to improve measurement repeatability, reliability, and speed. We have implemented an automated identification of multi-cell (3 and 9-cell) cavity passband modes. We also develop a software suite to configure the LLRF system via EPICS. This software is used to automatically measure the quality factor and accelerating gradient of cavities during VT.

Speaker: Eric Viklund (KEK)

15:00 Status of SRF cavity tuner for the ILC prototype cryomodule being built at KEK

An ILC prototype cryomodule is currently under construction at KEK. It incorporates eight superconducting 1.3 GHz TESLA cavities. Precise setting and maintenance of the resonance frequency of these narrow-band cavities before and during operation require dedicated cavity tuners. The tuner design is based on the LCLS-II tuner. However, the specific requirements of the ILC prototype cryomodule, together with the current market situation, led to an almost complete re-engineering of the tuner. Due to limited resources, comprehensive system-level testing prior to deployment is not feasible. Therefore, dedicated qualification tests of the individual components are being carried out. This contribution reports on the current status of tuner development and production. In addition, two novel test methods for the slow actuator (stepper motor with gearbox) and the fast actuator (piezo actuator) under cryogenic vacuum conditions are presented, together with first measurement results.

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

15:20 Discussion

Speaker: Yasuchika Yamamoto (KEK)

14:00 → 15:30 Tracking, Vertexing and Timing

15:30 → 16:00 Coffee break

16:00 → 17:30 Beam dynamics; beam delivery systems, main linacs, damping rings

16:00 → 17:30 Higgs and Electroweak

16:00 Impact of model-independent higher-order contributions to the Higgs-boson self-couplings

In this talk, I will point out the relevance of a new class of model-independent higher-order contributions to the trilinear and quartic self-couplings of the detected Higgs boson giving rise to potentially large effects of physics beyond the Standard Model (SM). It consists of SM-like diagrams with insertions of loop-corrected values for the trilinear and quartic Higgs self-couplings. While up to now predictions in specific models of physics beyond the SM were only evaluated up to the one-loop or, in some cases, up to the two-loop level, potentially large higher-order contributions can consistently be incorporated into existing one-loop or two-loop predictions. These model-independent higher-order contributions therefore improve the existing predictions that were obtained in specific models. Confronting the predictions with the relevant experimental results and theoretical constraints, a simultaneous determination of the trilinear and quartic Higgs-boson self-couplings is performed. The new set of model-independent higher-order contributions can then induce sizeable shifts in the inferred bounds on the trilinear and quartic Higgs self-couplings. For example, including the new higher-order corrections can shift the upper bound on the trilinear self-coupling modifier entering the theoretical predictions to $\sim4.9$, from the experimental limit of $6.1$. The results demonstrate that incorporating these higher-order contributions is essential for a consistent interpretation of present and future measurements. I will finally present a public tool that implements these effects and enables direct comparison with experimental limits.

Speaker: Dr Johannes Braathen (DESY)

16:18 WW-fusion in a ZHH analysis

The Higgs self-coupling measurement is an absolute must-have for establishing the Higgs mechanism experimentally. The Higgs self-coupling can be accessed at tree level through double Higgs production. In $e^+e^-$ collisions at 550 GeV, the dominant production mode is double Higgs strahlung with the ZHH final state, where the analysis projects a discovery reach on the Higgs self-coupling. A small but complementary contribution from vector boson fusion of the W-boson (WBF) to the vvHH final state ensures the discovery reach across a wide range of BSM scenarios. In this contribution, extracting the WW-fusion contribution from the ZHH production will be laid out, discussing the separation of WBF and ZHH from generator level to reconstruction level, as well as the interpretation of the two components contributing to a common signal.

Speaker: Julie Munch Torndal (DESY)

16:36 Latest news on the Higgs self-coupling prospects at 550 GeV with ILD

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The Higgs sector represents one of the least well-measured areas of high-energy particle physics. A key interest lies in the measurement of the Higgs self-coupling $\lambda_{HHH}$, which would establish the mechanism of electroweak symmetry breaking. This contribution follows last year's input to the European Strategy for Particle Physics Update (ESPPU), which extrapolated the sensitivity to $\lambda_{HHH}$ via $\mathrm{e}^+\mathrm{e}^- \to \mathrm{ZHH}$ at a Linear Collider Facility (LCF) operating at the elevated $\sqrt{s} = 550$ GeV with the International Large Detector (ILD), together with a full re-analysis of the $\mathrm{Z} \to \mathrm{e}^+\mathrm{e}^-/\mathrm{\mu}^+\mathrm{\mu}^-$ channels. Here we present our latest improvements: the inclusion of the $\mathrm{Z} \to \mathrm{\nu}\bar{\mathrm{\nu}}$ channel, a first look at the $\mathrm{Z} \to \mathrm{q}\bar{\mathrm{q}}$ and $\mathrm{Z} \to \mathrm{\tau}^+ \mathrm{\tau}^-$ channels, a more elaborate extraction of $\lambda_{HHH}$ and an explicit study of beyond-the-Standard-Model (BSM) cases. These analyses take into account an extensive range of Standard Model backgrounds and employ dedicated algorithms for event reconstruction and analysis; in particular, we make use of hard-scattering matrix elements for background rejection and machine learning for jet flavor tagging, overlay rejection and multi-class event classification.

Speaker: Bryan Bliewert

16:54 High energy probes of Higgs self-coupling via W boson fusion at future lepton colliders

I will discuss the sensitivity to the Higgs self-coupling through $W$ boson fusion di-Higgs production at $e^-e^+$ collider at $\sqrt{s}=3$ TeV (arXiv:2608.05096). The interplay between the Higgs self-coupling modifier ($\kappa_{\lambda}$) and Higgs-gauge boson coupling modifiers ($\kappa_{V}$ and $\kappa_{2V}$) within the $\kappa$ framework, will be discussed. The separation between signal and background will be carried by graph neural network (GNN) based classifier that achieves a signal significance of $\mathscr{Z}\approx 20~\sigma$ at $5~\mathrm{ab}^{-1}$.

Speaker: Dr Amir Subba (Wilczek Quantum Center, SIAS, USTC)

17:12 Exploring the Higgs potential at e+e- and photon-photon colliders

While in present experimental determinations of the trilinear Higgs-boson self-coupling often all other coupling modifiers are set to their Standard Model values, it is important to take into account the impact of all coupling modifiers or EFT operators that are not well constrained by the single Higgs production processes. Incorporating the dependence on the relevant other coupling modifiers, the prospects for determining the trilinear Higgs-boson self-coupling at the HL-LHC, an e+e- Linear Collider with a c.m. energy of at least 550 GeV and a photon-photon collider with a c.m. energy of 270 GeV or 380 GeV are compared with each other. The results differ significantly from the case where only the modifier of the trilinear Higgs-boson self-coupling is allowed to float. The implications for the physics capabilities of the different colliders are discussed.

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

16:00 → 17:55 Joint: Beyond Colliders and BSM

16:00 Recent news on muon physics

I plan to review the recent updates in the following topics related with muon;
- Dipole Moments
- charged Lepton Flavor Violation
- muon cooling & acceleration
- high-intensity muon beam
- applications

Speaker: Tsutomu Mibe (KEK)

16:25 Dark-Sector Theory Overview

Speaker: Felix Kahlhöfer (KIT)

16:50 Dark-sector searches at ILC beam dumps

Light dark-sector particles may be produced in electron and positron beam dumps at the International Linear Collider (ILC). We propose an experimental setup to search for such particles, the Beam-Dump eXperiment at the ILC (ILC-BDX). This talk provides an overview of future dark-sector searches at ILC-BDX, considering several benchmark scenarios, including axion-like particles and sub-GeV dark matter. In particular, we highlight the projected sensitivity and key features of ILC-BDX-type experiments.

Speaker: Daiki Ueda

17:15 NA64-like Experiments

Speaker: Sergei Gninenko (Millennium Institute for Subatomic Physics at High Energy Frontier (CL))

17:35 SHiP-like Experiments

Speaker: Maksym Ovchynnikov (CERN)

16:00 → 17:30 Joint: Software and AI Applications

16:00 → 17:30 Superconducting RF Systems

16:00 ITN-EU activities

The ITN-EU collaboration coordinates European activities for the development and industrialization of SRF cavities for the ILC, in close relation with KEK and international partners. The presentation will provide the latest status of the single-cell and 9-cell cavity activities, covering material qualification, fabrication, and surface treatment. The presentation will also outline the next steps and future R&D programme, aimed at improving cavity performance, reducing production costs and strengthening the industrial readiness of European SRF technology.

Speaker: Karl-Martin Schirm

16:20 Plasma Processing of Elliptical Cavities at INFN LASA

Plasma processing is increasingly recognized as an effective technique for mitigating field emission and restoring the performance of superconducting radiofrequency (SRF) cavities. A collaboration among the Commissariat à l'énergie atomique et aux énergies alternatives (CEA), the European Spallation Source (ESS), the Fermilab (FNAL) and the Istituto Nazionale di Fisica Nucleare (INFN-LASA) is currently working to adapt and optimize this method for the treatment of SRF elliptical cavities.
This contribution summarizes the ongoing efforts at INFN LASA toward implementing plasma processing both in fully assembled cryomodules and in cavities prepared for vertical testing. We present the first experimental results obtained on a ESS medium-beta 704 MHz cavity equipped with different couplers and on a PIP-II low-beta 650 MHz cavity equipped with the Fundamental Power Coupler.

Speaker: Elisa Del Core (INFN Milano - LASA)

16:40 Analysis of HOM Power Propagation and Absorption in the PERLE String

PERLE (Powerful Energy Recovery Linac for Experiments) is designed to demonstrate multi-turn, high-current operation of an Energy Recovery Linac (ERL). Achieving this demanding operating regime requires effective management of propagating higher-order-mode (HOM) power in order to limit beam instabilities and minimize the associated cryogenic heat load. The PERLE main cryomodule comprises four 5-cell superconducting cavities operating at 801.58 MHz. Each cavity is equipped with two HOM hook couplers, while cold beamline absorbers operating at 40 K are positioned between neighboring cavities, with tapered transitions at both ends of the cavity string. This work presents updated results of the HOM power spectrum of the complete multi-cavity string under the nominal PERLE beam current and filling pattern. The resulting dielectric losses in the cold beamline absorbers are also evaluated. The analysis provides the distribution of HOM power among the different ports of the string and supports the assessment of the HOM damping scheme for high-current operation.

Speaker: Axel Perez Ruiz (Université Paris-Saclay, CNRS/IN2P3, IJCLab)

17:00 Commissioning of ESS superconducting linac in preparation for beam on target

In this talk will be presented the technical commissioning of ESS superconducting linac, challenges and outcomes are presented

Speaker: Dr Cecilia Maiano (European Spallation Source)

17:20 Discussion

Speaker: Yasuchika Yamamoto (KEK)

Wednesday 11 November

09:00 → 09:40 Plenary: Plenary Wed-1

09:00 AI and physics (title TBD)

Speaker: Koji Hashimoto

09:40 → 11:10 Sustainability

09:40 Towards Standardized Sustainability Assessment of Accelerator Research Infrastructures

Accelerator-based research infrastructures are among the most scientifically productive facilities worldwide, but their operation is also associated with significant energy demands, resource consumption, and environmental impacts. As future accelerator facilities pursue increasingly ambitious scientific and technical goals, the need for transparent and quantitative approaches to sustainability assessment is becoming increasingly important.
This contribution presents a framework for the standardized assessment of sustainability in accelerator research infrastructures, developed within the context of the European project Research Facility 2.0 (RF2.0). The framework focuses on environmental sustainability while maintaining links to operational and scientific performance. It organizes sustainability assessment into the domains of resources, energy, and greenhouse-gas emissions, and introduces a set of quantifiable indicators that enable systematic evaluation of facilities, technical systems, and alternative design solutions. A distinctive feature of the methodology is the incorporation of scientific output and operational time as normalization parameters, thereby connecting sustainability performance directly to the mission of research infrastructures. The framework further supports aggregation into composite sustainability scores while preserving transparency and traceability of individual indicators. The presentation will summarize the rationale behind the proposed metrics, their mathematical structure, and their application to accelerator technologies and infrastructure-level assessments.
In addition, selected insights from international sustainability studies involving research infrastructures and accelerator facilities will be discussed, highlighting common priorities, opportunities for energy efficiency improvements, and emerging approaches for integrating sustainability considerations into future facility planning and operation.

Speaker: Falastine Abusaif (KIT)

10:10 Environmental Impact and Considerations for Future Accelerators: 2nd LDG Mandate

Speaker: Caterina Bloise (INFN e Laboratori Nazionali di Frascati (IT))

10:30 IHEP Activities on Sustainability

The Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, is actively developing sustainable technologies for future particle accelerators, with the goal of reducing energy consumption and improving overall energy efficiency. Our activities cover a broad range of accelerator technologies, including superconducting radio-frequency (SRF) cavities, permanent-magnet systems, high-efficiency RF power sources, energy-recovery power supplies, and energy-recovery RF loads.

For SRF accelerators, we are investigating technologies to improve cryogenic efficiency and reduce the overall power consumption of accelerator facilities. Permanent magnets are being developed as an alternative to conventional electromagnets, offering significant potential for reducing power consumption and simplifying accelerator operation. High-efficiency klystrons and other RF power sources are being developed to achieve higher wall-plug efficiency, with energy-recovery technologies further improving RF system efficiency.

In addition, IHEP is exploring heat-recovery technologies to reuse waste heat generated by accelerator facilities, including the recovery and utilization of hot water. Energy-recovery power supplies and energy-recovery RF loads are also being studied to recover otherwise wasted electrical and RF energy.

These efforts aim to establish an integrated approach to sustainable accelerator design and operation, contributing to the development of greener, more energy-efficient, and economically sustainable future large-scale accelerator facilities.

Speaker: Zusheng Zhou (IHEP)

10:50 Potential Value of Tohoku as a Renewable Energy Hub

To realize "Green ILC" in Kitakami Site, it is crucial that abundant renewable sources in Tohoku Area will be highly utilized under triple helix collaboration. In this presentation, the presenter will give a talk on (ⅰ) attractiveness of Tohoku Area in the context of pursuing sustainability, (ⅱ) challenges from the view of renewables developer, and (ⅲ) how we should get through the challenges with interdisciplinary approach, based on my own hands-on experiences in large-scale onshore wind project in Iwate Prefecture.

Speaker: Ryotaro Amano (Japan Advanced Institute of Science and Technology (JAIST))

11:10 → 11:30 Coffee break

11:30 → 13:30 Industry and Applications

11:30 Beyond a Single Project: Connecting ILC and Frontier Science Projects to Drive Industrial Innovation in Tohoku, Japan

Tohoku, northeastern Japan, is home to several major science and technology initiatives, including the International Linear Collider (ILC), NanoTerasu, the ITER Broader Approach (BA) activities, and the Fukushima Innovation Coast Framework. These projects provide local companies with opportunities to acquire advanced technologies, knowledge, and connections with researchers and research institutions.

However, participation in frontier science projects does not automatically lead to new products, new markets, or sustained business growth. Based on a survey of 47 companies in the Tohoku region, we identified two critical gaps in the process of translating frontier science into industrial value: (1) the acquisition and strengthening of R&D capabilities, and (2) the development of market creation and commercialization capabilities.

This suggests that the key challenge is not simply attracting individual frontier science projects, but creating connections among projects, companies, universities, research institutions, startups, and talent across the region.

The Tohoku Economic Federation is therefore exploring a regional innovation system in which ILC and other frontier science projects reinforce one another, while supporting the upgrading of regional companies, the concentration of R&D functions, and the circulation of highly skilled talent.

This presentation will introduce the Tohoku approach and discuss how regional coordination can help transform frontier science investments into sustained industrial innovation, business growth, and international collaboration.

Speaker: Eisaku Nishiyama (Tohoku ILC Promotion Council)

11:50 FULLCRYO is poised to deliver solid industrial equipment support for the construction of CEPC.

As CEPC-SppC Industrial Promotion Consortium, CIPC is an
industrial collaborative organization established for the CEPC
project, with nearly 100 member entities. The consortium aims to
jointly tackle key technologies and promote the industrialization
of research achievements, facilitating the high-quality
development of China’s industrial manufacturing, technology
R&D and engineering systems. This report outlines the founding
background, development vision and organizational structure of
CIPC, and presents the latest progress made by its member units
in booster, collider ring, MDI, civil engineering,
superconductivity, cryogenics, vacuum and other fields, so as to
comprehensively demonstrate the current status of CIPC.
Driven by the global fusion industry, China’s industrial
manufacturing and engineering capabilities have advanced
rapidly, which will provide strong support for the industrial
supporting construction of CEPC. Especially in the cryogenic
field, FULLCRYO from China stands as a pioneering enterprise,
has specialized in 20K-2K large-scale cryogenic equipment and
technical services. It has delivered more than 40 sets of large￾scale hydrogen-helium cryogenic equipment, covering 40 L/h, 70
L/h and refrigerators with power ratings of 400 W, 500 W, 850 W,
1 kW, 2 kW, 4 kW and 18 kW. The products have been deployed
in major scientific facilities and hydrogen energy projects, and
can meet the development demands of cutting-edge high-end
sectors including controlled thermonuclear fusion, particle
accelerators, hydrogen energy, semiconductors and quantum
technology.

Speaker: Jinlin Gao (Beijing Sinoscience Fullcryo Technology Co.,Ltd)

12:10 Fostering Industrial Accelerator Impact: From Compact ICS Sources to SRF Cavities

RadiaBeam Technologies recently commissioned a compact Inverse Compton Scattering (ICS) facility based on 100 MeV linac. The ICS source employs a hybrid photoinjector achieving sub-picosecond bunch compression within a very compact footprint. The high brightness beam is injected into a pair of high gradient C-band linac modules to achieve ICS photon flux output tunable in the range of 30 – 180 keV. We will present the ICS source architecture and commissioning milestones, along with the development and implementation of the high-power versatile C-band RF infrastructure, directly relevant to the broader needs of the collider developers.
In parallel, RadiaBeam has undertaken superconducting radiofrequency (SRF) cavity development efforts targeting next-generation accelerator applications. Recent work includes a scaled spoke cavity design and early-stage manufacturing, with a strategic focus on re-establishing domestic industrial SRF fabrication capabilities in the United States. The common collaborative threads connecting these seemingly disparate endeavors will also be discussed as path toward successful industrial engagement.

Speaker: Mr Ronald Agustsson (RadiaBeam)

12:30 Spanish Industry for Big Science: Capabilities, Collaboration and Success Stories

Future accelerators are major scientific and also industrial challenges. Turning ambitious concepts into reliable machines requires companies capable of designing, manufacturing, integrating and validating highly complex, often one-of-a-kind systems.

Over the last decades, Spain has developed a mature and highly specialised Big Science industrial ecosystem, with proven experience in some of the world's most demanding scientific facilities.

This talk will present some representative examples of these capabilities and, above all, an invitation to the international accelerator community to share their technological challenges: Spanish industry are experts in co-creation and eager to collaborate, transforming demanding specifications into working hardware.

Also, the talk will introduce INEUSTAR (the Spanish Science Industry Association) as a gateway to the Spanish Science Industry, helping research organisations and international partners identify the right industrial capabilities for their technological needs.

Speaker: Dr Leonor Mendoza (INEUSTAR / INDUCIENCIA)

12:50 Activities of the Advanced Accelerator Association (AAA)

The Advanced Accelerator Association (AAA) is a Japanese non-profit organization dedicated to promoting advanced accelerator science and technology through collaboration among industry, academia, and government. Since its establishment in 2008, AAA has supported accelerator-related initiatives, including the International Linear Collider (ILC), while fostering industrial participation and public outreach. AAA organizes technical committee activities, symposiums, and international exchanges to strengthen cooperation among stakeholders. This presentation provides an overview of AAA’s recent activities and discusses its efforts to advance accelerator technologies and promote international collaboration within the global accelerator community.

Speaker: Masanori Matsuoka (MHI/AAA)

13:10 Advanced Ceramic Technologies for Future Accelerators at Kyocera Corporation

Kyocera Corporation has been providing advanced components to leading accelerator facilities worldwide, based on its long-established expertise in ceramic and metallization technologies. The company has an extensive record of supplying components to major accelerator laboratories and research institutes, including KEK, CERN, Jefferson Lab , Fermi Lab , BNL ,and HEPS. In this presentation, we will introduce Kyocera's accelerator-related products and present our latest technological innovations.

Speaker: Mr Chihiro Sakamoto (KYOCERA Corporation)

13:20 Recent activities of MHI-MS in Accelerator Technologies

Mitsubishi Heavy Industries Machinery Systems, Ltd. (MHI-MS) has extensive experience in the design and fabrication of accelerator components for major scientific facilities in Japan and worldwide. This presentation will highlight recent activities of MHI-MS, with a focus on superconducting and normal-conducting accelerator components, including RF cavities, accelerating structures, and related systems. Manufacturing capabilities, project achievements, and future prospects will also be presented.

Speaker: Nobuyuki Shigeoka (Mitsubishi Heavy Industries Machinery Systems, Ltd.)

13:30 → 14:30 Lunch

14:30 → 16:00 Beam dynamics; beam delivery systems, main linacs, damping rings

14:30 → 16:00 Beyond Colliders Opportunities

14:30 → 16:00 Calorimetry + Particle ID

14:30 Operation and Performance of the ATLAS Tile Calorimeter in LHC Run 3

The Tile Calorimeter (TileCal) is a sampling hadronic calorimeter covering the central region of the ATLAS experiment, using steel as the absorber and plastic scintillators as the active medium. The scintillation light is collected by wavelength-shifting fibres and read out by photomultiplier tubes (PMTs). The analogue signals are amplified, shaped, digitized at 40 MHz and stored on the detector until a trigger decision is received. The TileCal front-end electronics reads out the signals produced by about 9852 channels, measuring energies ranging from about 30 MeV to about 2 TeV.

The detector response is continuously monitored and calibrated at each stage, from scintillation light production to signal reconstruction. During the LHC Run 3, high-momentum isolated muons have been used to validate the electromagnetic energy scale, while isolated hadrons provide complementary studies of the hadronic response. The calorimeter time resolution is evaluated using multi-jet events.

This contribution presents the latest TileCal performance and operational experience from the LHC Run 3, including calibration, detector stability, absolute energy scale, response uniformity and time resolution.

Speaker: Helena Santos (Laboratory of Instrumentation and Experimental Particle Physics (PT))

14:50 A First Look at the Future of the ATLAS Tile Calorimeter: Phase-II Demonstrator Design and Performance in Run 3

The Tile Calorimeter (TileCal), the central hadronic calorimeter of the ATLAS experiment at the Large Hadron Collider (LHC), is undergoing a major Phase-II upgrade to meet the challenging requirements of the High-Luminosity LHC (HL-LHC). The upgrade introduces a completely redesigned electronics architecture to cope with trigger rates of up to 1 MHz, increased radiation levels and higher pile-up conditions, while improving the detector’s maintenance flexibility and performance.

As part of the extensive research and development programme, a Phase-II Upgrade Demonstrator module was constructed in 2014, implementing the new electronics architecture while maintaining backward compatibility with the existing ATLAS Trigger and Data Acquisition systems. Following successful validation in CERN test beam campaigns, the Demonstrator was installed in the ATLAS detector in 2019 and operated under collision conditions in Run 3 (2022-2026). Its operation provided a unique opportunity to evaluate the upgraded hardware and software in a realistic experimental environment over an extended period.

This contribution presents the design and development of the Phase-II Demonstrator, including its upgraded electronics and software, and discusses its operational experience and performance during Run 3. The results from collision data demonstrate the stability and reliability of the upgraded system, providing valuable input for the final design, integration and commissioning of the TileCal Phase-II upgrade for the HL-LHC.

Speaker: Eduardo Valdes Santurio (Stockholm University (SE))

15:10 ATLAS Tile Calorimeter Upgrades for the High-Luminosity LHC Era

The ATLAS Tile Calorimeter (TileCal) is a sampling hadronic calorimeter in the central region of the ATLAS detector, consisting of steel absorber plates interleaved with plastic scintillator tiles. The High-Luminosity phase of the LHC (HL-LHC), expected to begin in 2030, will deliver an instantaneous luminosity up to 7.5 times the LHC nominal value. To meet the requirements of a 1 MHz trigger rate, increased radiation levels, and higher pile-up, the TileCal on- and off-detector electronics will be replaced during the 2026–2030 shutdown.

In the upgraded system, signals from every TileCal channel will be digitized at 40 MHz and transmitted directly to the back-end electronics, where they will be reconstructed and provided to the first-level trigger. This architecture will improve the precision of calorimeter information available to the trigger and enable more sophisticated trigger algorithms. The modular front-end electronics feature radiation-tolerant commercial off-the-shelf components and redundant design to minimise single points of failure. Timing, control, and data communication are implemented using modern field-programmable gate arrays (FPGAs) and high-speed optical links operating at up to 9.6 Gb/s.

The TileCal Phase-II upgrade programme has been supported by an extensive R&D and test-beam programme. This contribution presents the ongoing development of the on- and off-detector electronics, their expected performance and results from test-beam campaigns with electronics prototypes, as well as the optics robustness studies.

Speaker: Seyedali Moayedi (University of Texas at Arlington (US))

14:30 → 16:00 Flavor, Top and QCD

14:30 Probing CP violation in (e^+e^- \to t\bar tH) at a 550 GeV Linear Collider with Machine-learned Observable

The observed matter–antimatter asymmetry of the Universe motivates searches for new sources of CP violation beyond the Standard Model. The Higgs interaction with the top quark, the heaviest known elementary fermion, provides a particularly well-motivated place to search for such effects. A high-energy linear (e^+e^-) collider offers a clean and well-defined initial state, controllable beam polarisation, and the possibility of reconstructing the complete (t\bar tH) final state. In previous studies of (ZH) production, machine-learned CP observables were found to provide improved sensitivity compared with conventional angular observables. Motivated by this result, we investigate whether a similar strategy can exploit the more complex CP information in (t\bar tH), taking advantage of recent developments in event reconstruction and flavour tagging for the ILC.

We present an analysis of (e^+e^- \to t\bar tH) at (\sqrt{s}=550) GeV, using Physsim event generation including the near-threshold NRQCD enhancement and SGV fast detector simulation. The study focuses on semileptonic (t\bar tH) events with (H\to b\bar b). The implementation of Particle Transformer flavour tagging in the ILC reconstruction provides improved heavy-flavour identification as well as charge- and flavour-sensitive information for the reconstructed jets. This information is used both in jet assignment and in the construction of CP-sensitive observables, while also improving multivariate signal-background discrimination. Samples with fully polarised (e^-_Le^+_R) and (e^-_Re^+_L) initial states are studied separately and subsequently combined according to a realistic longitudinal-polarisation running scenario for a future linear collider.

We investigate complementary strategies for extracting the CP-odd scalar–pseudoscalar interference. For physically motivated angular observables, different choices of spin analysers, charge and flavour ordering, and reference-frame definitions are explored. Their generator- and reconstruction-level sensitivities are compared directly, exposing information losses associated with detector reconstruction and ambiguities in identifying the relevant decay products. In parallel, a machine-learned CP observable is constructed directly from reconstructed event information. We explore different choices of input features and event representations, ranging from the kinematics of a minimal set of reconstructed spin analysers to representations incorporating both W-daughter jets, charge-aware flavour information, assignment quality, kinematic-fit quantities, invariant masses, and the fitted neutrino. The resulting angular and machine-learned observables are compared using their sensitivity to the CP-odd interference.

Speaker: Yuyang Zhang (University of Glasgow)

14:50 Disentangling new physics with quantum entanglement in top-pair production at future lepton colliders

We investigate quantum entanglement and Bell-inequality violation in top-antitop pair production at future lepton colliders. We examine how those in the SM are modified in several well-motivated extensions of the SM:(i) a neutral scalar mediator that couples to charged leptons and top quarks via Yukawa interactions and contributes as an additional s-channel exchange; (ii) the minimal gauged U(1)B-L model, which introduces a new neutral gauge boson Z' coupling vectorially to SM fermions; and (iii) a Randall-Sundrum scenario, in which the exchange of massive Kaluza-Klein gravitons arising from a warped extra dimension induces additional spin-dependent interactions.

Speaker: Prof. Kentarou Mawatari (Iwate U.)

15:10 Experimental prospects for quantum decoherence measurements at colliders

Quantum entanglement is one of the defining features of quantum mechanics. In high-energy colliders, quantum properties are experimentally accessible, the most important example being top quark pair production at the LHC. This channel led to the discovery of spin entanglement in 2024 [1-2].

In this work [3], we study how energetic final-state radiation modifies the spin entanglement of fermion–antifermion pairs and demonstrate that it can lead to measurable decoherence. The study is performed at parton level using simulations computed with MadGraph5_aMC@NLO, using $t\bar{t}g$ and $\tau^+\tau^-\gamma$ production processes. The spin density matrix is reconstructed as a function of the FSR energy.

We conclude that a statistically significant observation of decoherence can be obtained with current data in associated $pp\to t\bar{t}g$ production at the LHC and in $e^+e^-\to\tau^+\tau^-\gamma$ production at Belle II. Future electron-positron colliders operating well above the $t\bar{t}g$ production threshold or at the Z pole, respectively, could further enable differential measurements of quantum entanglement as a function of the FSR energy.

[1] ATLAS Collaboration. Nature 633, 542 (2024).
[2] CMS Collaboration. PRD 110, 112016 (2024).
[3] Aoude et al. arXiv:2604.16268v3. Submitted to PRL.

Speaker: Guillermo Garcia Mir (Univ. of Valencia and CSIC (ES))

14:30 → 16:00 High Gradient RF Techniques

14:30 Status of the COLD (Cool copper Operation Linac) Project

The ESRF long-term plan for the upgrade of the injection complex foresees a full 6 GeV energy linac option. Given the space limitations of the site, the linac must fit in < 140 m, compactness is a strong design constraint. The most promising candidate to fulfill this goal is the C2 (Cool Copper at 77 K) technology in C-Band (5.712 GHz). The COLD Project intends to demonstrate the readiness of such a technology by accelerating a beam produced by a S-Band RF Gun (2.998 GHz) using C2 structures. The Project officially started in April 2025 and the first civil works of the installation started this summer. The status and goals of the Project will be reported.

Speaker: Alessandro D'Elia (ESRF)

14:50 Update on C-band activities at LANL

This talk will report on the status of C-band research activities at Los Alamos National Laboratory. This includes commissioning of the Cathodes And Radio-frequency Interactions in Extremes (CARIE) high gradient C-band RF photoinjector test stand and design and fabrication of the high-gradient C-band proton acceleration structures. We are testing functionality of the CARIE test stand by conditioning the high gradient photoinjector capable of producing electric fields at the cathode up to 250 MV/m. The photoinjector is powered by a 50 MW, 5.712 GHz
Canon klystron. The all-copper photoinjector is fabricated and cold-tested and undergoes high gradient testing which is likely to finish this Fall. We have also designed and are fabricating a four-cell high gradient C-band accelerating structure for the LANSCE accelerator booster designed to accelerate beta=0.93 protons to the final energy of 3 GeV. The structure will have to be tested at cryogenic temperatures which requires infrastructure updates at CARIE. Finally, at the C-band Engineering Research Facility (CERF-NM), we recently finished the high
gradient testing of the C-band cavity with nickel-chromium higher order mode absorbers. We are conducting the post-mortem inspection of the cavity to evaluate the effects of high gradient on the nickel-chromium absorbing material. The statuses of the CARIE facility, CERF-NM facility, their high-power operation, and the results of various high gradient tests will be presented.

Speaker: Evgenya Simakov (LANL)

15:10 High-Power Test Results for Multiple-Sector X-band Accelerating Structures Fabricated Using Different Materials but Based on the Same Design

Multiple-sector X-band accelerating structures were designed and fabricated with four quadrants [Nucl.Instrum.Meth.A 1063 (2024), 169272]. We carried out high-power tests at Nextef2, an X-band high-power test stand in KEK, for two such test cavities fabricated using hard pure-copper and copper-silver with the same electrical design. We report the results of the tests and postmortem investigations, including comparison between the two cavities.

Speaker: Abe Tetsuo (KEK)

14:30 → 16:00 Superconducting RF Systems

14:30 The investigation of the manufacturing methods for 1.3 GHz 9-cell cavity under the International Linear Collider Technology Network(ITN)

As a part of research for the manufacturing methods for SRF cavities used in ILC(International Linear Collider), collaborative research is conducted in the framework of the ITN(ILC Technology Network) which includes the Korea University and KEK. Following our previous study on 1.3 GHz single-cell niobium cavities, we have extended our manufacturing scope to full-scale 1.3 GHz 9-cell cavity for ILC in collaboration between the Korea University and KAT. To validate the tooling, jigs and baseline manufacturing procedures, 1.3 GHz 9-cell cavity has been initially fabricated by using copper material. Room-temperature RF measurements and bead-pull test have been conducted, confirming precise field-flatness tuning and assembly accuracy. Building on these results, we are currently manufacturing the 1.3 GHz 9-cell cavity with niobium material. The cavity fabrication in Korea is scheduled for completion by June 2027, followed by surface treatment and vertical test at KEK in Japan. We present the VT results of 1.3 GHz single-cell cavities, the fabrication results of copper prototype cavity, and the progress of the niobium 1.3 GHz 9-cell cavity fabrication.

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

14:50 Progress of High-current Superconducting Cavity Cryomodule at IHEP

Energy recovery linac (ERL) based EUV-FELs are among the most promising candidate technologies for next-generation lithography. The development of a 10-mA high-current injector cryomodule for ERL-FELs has been initiated. The cryomodule consists of three 1.3 GHz 2-cell superconducting cavities, which are designed to accelerate 10 mA electron beam to 10 MeV. The cavities will receive the process of mid-temperature furnace baking, to reach the specification of Q₀ = 3×10¹⁰ at 17.4 MV/m (@ 2.0K). The shape of 1.3 GHz TESLA cavity is reference for these 1.3 GHz 2-cell cavities, which adopt the beam pipe with large aperture. Therefore, all higher-order modes (HOMs) can propagate along the large pipe and be absorbed at ~40K. The dipole-mode impedance is well below the beam breakup (BBU) threshold in the simulation, with this damping scheme. Each cavity is equipped with two fundamental power couplers (FPC), which suppresses the effect of transverse kick on the beam. In addition, the multipacting effect and the mechanical performance of the cavity have been evaluated, and both meet the design requirements. Four 1.3 GHz 2-cell cavities have just been fabricated, which will be subjected to post process and vertical test soon.

Speaker: Rui Ge (IHEP，CAS)

15:10 Fabrication and Radiofrequency Characterization of 1.3 GHz TESLA-type 9-Cell Copper Prototype Cavities

This study presents the fabrication and room-temperature radiofrequency (RF) characterization of 1.3 GHz TESLA-type 9-cell copper prototype cavities as a preparatory step toward future niobium superconducting RF cavity development. Prior to fabrication, three-dimensional electromagnetic simulations were performed to evaluate the resonant frequency, TM010 passband characteristics, and axial electric-field distribution. Based on the simulation results, three copper prototype cavities were fabricated and examined through helium leak testing and preliminary RF measurements. One cavity, in which all nine passband modes were clearly identified, was selected for detailed RF characterization. Vector network analyzer measurements showed an initial TM010 π-mode resonant frequency of 1.297913 GHz. The axial electric-field distribution was subsequently evaluated using bead-pull measurements, followed by repeated frequency-correction calculations and mechanical tuning. As a result, the field-flatness metric was improved from 35.45% to 95.9%, confirming a substantially more uniform field distribution among the nine cells. These results experimentally validate an integrated workflow consisting of cavity fabrication, room-temperature RF measurement, bead-pull characterization, and mechanical tuning. The established procedure provides a practical basis for the future fabrication and RF evaluation of 1.3 GHz niobium superconducting cavities.

Speaker: Seongjae Choi (Korea University)

15:30 Research Progress on 1.3 GHz High-Gradient Superconducting Cavity and cryomodule at IHEP

Speaker: Dr MI ZHENGHUI (IHEP)

15:50 Discussion

Speaker: Yasuchika Yamamoto (KEK)

16:00 → 16:30 Coffee break

16:30 → 18:00 Beyond Colliders Opportunities

16:30 Future Linear Colliders as High-Energy Inverse Compton Photon Sources for Photon Science

Inverse Compton scattering (ICS) is today a well-established route to produce tunable, high-brilliance photon beams for photon science, nuclear physics and fundamental studies. Pushing ICS sources towards higher photon energies requires electron beams in an energy range that only large-scale accelerator facilities can provide. Future linear colliders offer electron beams with energies extending from hundreds of GeV to the TeV scale, opening opportunities beyond their primary role as particle colliders. This activity is developed in natural synergy with analogous studies already carried out and ongoing for circular colliders, in particular the FCC-ee. We explore the use of these beams to generate high-energy photon radiation through inverse Compton scattering. As a benchmark, the LCF380 scenario with 190 GeV electrons is considered, using laser pulses synchronized with the electron bunches to provide the photon target for Compton interactions. The photon spectrum, yield, angular distribution and flux are studied as a function of the electron-beam and laser parameters. The study investigates the potential for producing intense and energetic photon beams, as well as possible configurations with multiple Compton interaction points along the linear accelerator. Finally, the scaling of the concept towards TeV-class linear colliders and its potential applications in photon science, nuclear physics and high-energy photon physics are discussed.

Speaker: Illya Drebot

16:50 Can electrons emit photons of energy larger than their own? Full Inverse Compton Scattering

The newly discovered effect of Full Inverse Compton Scattering has shown several implications to unexpected phenomena, like the achievement of extremely high accelerations with electrons coming to a sudden stop from relativistic velocities, therefore showing potentialities of detecting Unruh radiation, and opening a portal towards quantum gravity, and like the emission of photons with energy larger than that of the emitting electron, in apparent violation of energy conservation. We will discuss these new findings with an eye at the historical development, throughout the last century, in the understanding of QED electron-photon interactions, from the nuclear bomb development to the first studies on cosmic rays, to the development of modern Inverse Compton Scattering advanced sources of X/gamma rays. Full Inverse Compton Scattering can have significant impacts also in other fields like plasma physics, with the capability of trapping electrons (positrons) in magnetic bottles, with the spectral purification of broadband gamma ray photon beams, and with several possibile implications in the field of gamma ray cosmic sources.
https://doi.org/10.1016/j.nima.2024.169964

Speaker: Luca Serafini (INFN - Milan)

17:10 Towards non-perturbative QED at a linear collider facility with plasma-mirror-boosted lasers

Strong-field quantum electrodynamics (QED) offers a unique window into fundamental physics at extreme electromagnetic fields, where higher-order effects may eventually lead to a breakdown of the perturbative description of QED. The recently launched NP-QED project aims to approach this regime by combining relativistic electron beams with ultra-intense laser pulses, intensified by Doppler-boosted plasma mirrors. Future linear collider facilities, providing electron and positron beams with energies extending into the TeV regime, could substantially extend the accessible strong-field parameter space. A particular focus is placed on combining plasma-mirror-boosted laser pulses with the 190 GeV electron beam of the LCF380 scenario. We discuss the strong-field regime accessible with such a setup and its potential for approaching the fully non-perturbative regime of QED.

Speaker: Ivo Schulthess (Deutsches Elektronen-Synchrotron (DE))

16:30 → 18:00 Beyond Standard Model

16:30 → 18:00 Electron/Positron Sources

16:30 Prototype Development of Key Components for a High-Intensity Positron Source

Development of a high-intensity positron source requires reliable components capable of operating under severe beam-loading, thermal, mechanical, and electromagnetic conditions. We are developing prototypes of three key components: a rotating positron production target, an accelerator structure for capturing and accelerating positrons, and a flux concentrator for providing a strong pulsed magnetic field near the target.

The rotating-target prototype has been completed and evaluated through rotation, vacuum, and thermal-load tests. This presentation reports its measured performance, together with the design concepts and fabrication status of the accelerator structure and flux concentrator. The remaining technical challenges and future plans toward improving the our prototype are also discussed.

Speaker: Mr Yu Morikawa (KEK)

17:00 A seamless Blackbox optimization of ILC E-Driven Positron source

Since the ILC (International Linear Collider) cannot reuse beams, it is necessary to generate a large number of particles. In Electron-driven positron sources, it is important to find efficient generation conditions because the target load becomes large. We simulated the process in which an electron beam is injected into a W-Re target, the generated positrons are captured and accelerated by RF, and then collected within the DR acceptance, and conducted research on more efficient positron generation and capture conditions. The parameters under consideration include various parameters of the positron accelerator. We adopted the Black Box optimization method. We report the current status.

Speaker: Yodai Sasaki

17:30 Beam Simulation and Parameter Study of the Capture Linac for the ILC E-Driven Positron Source

To achieve high luminosity in the International Linear Collider (ILC), we need a high-current multi-bunch beam. Maximizing the positron capture efficiency (yield) is a key challenge. Positrons go through capture and booster linacs before entering the damping ring. For good transport efficiency later, it is important not only to get many positrons, but also to make the bunch short during the capture stage. In this study, we simulated the beam behavior in the capture section of the ILC electron-driven positron source. This section includes a target, a flux concentrator (FC), a collimator, and solenoid-focused accelerating structures. Previous studies showed that beam loss at the collimator is the biggest issue, and the bunch length is mostly decided around the fourth accelerating structure. Based on this, we investigated how the component layout and magnetic field in the upstream region of the capture linac affect the yield and bunch length. We investigated the parameter dependencies to provide guidelines for efficient beam capture under realistic engineering constraints. In this presentation, we report these simulation results.

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

16:30 → 18:00 High Gradient RF Techniques

16:30 Next Generation Low Level RF Control Automated for Breakdown Studies

The radio frequency (RF) system on a chip (RFSOC) is a next generation low level RF board that integrates both direct RF sampling for data collection with local processing and algorithmic control with an FPGA for high precision RF outputs. The ability to directly sample RF inputs allows for local control of real-time frequency tuning and pulse shaping feedback of the RF output pulse. We use this system to control an S-band (2.856 GHz) klystron connected to a single S-band cavity to perform automatic breakdown statistics and conditioning. Here, we present the conditioning performed by the automatic RFSOC feedback and demonstrate the RFSOC as a compelling candidate for LLRF generation at future collider facilities.

Speaker: Sophia Morton (SLAC, Stanford)

16:50 Short Pulse Driven Photogun for Bright Beams generation

High gradient radio frequency (rf) driven photoguns are photoemission electron sources that have important applications for accelerator-based instruments, such as light sources and electron microscopy. Numerous efforts have been made to push for even higher field gradient while suppressing rf breakdowns. We propose the Compressed Ultrashort Pulse Injector Demonstrator, a 1.6 cell photogun driven by nanosecond high power rf pulses to achieve high gradients with low breakdown rate. This photogun is powered by ultrashort pulses from a rf pulse compressor and a high power klystron. This presentation focuses on the work of the CUPID photogun for generating bright electron beams to drive x-ray free-electron lasers (FELs) at 40 keV photons or higher. We first show the design of CUPID photogun, followed by its capability of bright beam generation when forming a photoinjector with a superconducting solenoid and downstream linacs. We then show start-to-end simulations of the existing LCLS copper accelerator free-electron laser with CUPID photogun as a drop-in replacement to demonstrate its improvement in delivering hard x-rays at mJ level pulse energy. Finally, we show preliminary high power rf testing of CUPID prototypes and plans for electron beam generation.

Speaker: Emilio Nanni (SLAC National Accelerator Laboratory)

16:30 → 18:00 Joint: Higgs/EW and Global Analysis

16:30 ILC, FCC-ee Precision Polarimetry with Difermion and Vector Boson Event Fits

Precision measurements, especially for integrated luminosity using diphotons, put strict demands on beam polarimetry at future e+e- colliders. This is strictest at the Z pole, where methods to achieve order 10^{-4} on polarimetry are needed. We entertain multiple scenarios for ILC and FCC-ee as the setting for this study. Paths towards order 10^{-4} on polarimetry using Difermion and vector boson containing events. Biases between event fits, such as from depolarization during beam collision, and Compton polarimeter measurements are also discussed.

Speaker: Brendon Madison (University of Kansas)

16:50 Assessing uncertainties in the determination of the trilinear Higgs self-coupling from single-Higgs observables

Probing the shape of the Higgs potential is a primary objective of the next generation of flagship particle physics experiments, for which measuring $\lambda_\mathrm{hhh}$, the trilinear Higgs self-coupling, will play a crucial role. Despite operating below the di-Higgs production threshold, circular $e^{+}e^{-}$ machines will still have indirect access to $\lambda_\mathrm{hhh}$ via its loop-level contributions to single-Higgs production observables. In this work, we investigate how well $\lambda_\mathrm{hhh}$ can be determined by such indirect effects within a global EFT fit. While most studies to date assume that future measurements will be compatible with SM predictions, here we consider non-SM values of $\lambda_\mathrm{hhh}$, using an inert doublet extension of the SM as an example of a New Physics scenario that could be realised in nature. We find that theory uncertainties related to the truncation of the EFT expansion and to higher-order corrections, which are often neglected, can substantially affect the resulting precision for $\lambda_\mathrm{hhh}$. Moreover, in order to investigate the impact of experimental noise on the fit results, we perform a series of toy studies where we smear the central values for the pseudo-measurements according to their projected experimental uncertainty.

Speaker: Murillo Rebuzzi Ardións Vellasco (University of Bonn (DE))

17:10 Probing SMEFT Effects in VBS Vh Production at TeV-Scale Lepton Colliders

We demonstrate that the Feynman-Diagram (FD) gauge provides a transparent decomposition of SMEFT contributions according to scattering mechanisms and gauge-Higgs interaction vertices, enabling a direct physical interpretation of Wilson-coefficient effects in electroweak scattering. Building upon this framework, we study SMEFT effects in Zh production associated with neutrinos at future TeV-scale lepton colliders. We investigate how dimension-six operators modify the individual amplitude contributions and their interference, and identify the phase-space regions and kinematic observables that are particularly sensitive to these effects. Our analysis illustrates how the FD gauge can be used to trace deviations from the Standard Model back to the underlying scattering mechanisms and interaction vertices.

Speaker: Hiroyuki Furusato (Iwate University)

17:30 Triple Gauge Couplings: Using Optimal Observables at the Detector Level

We perform optimal-observable-based fits to assess the statistical reach of future $e^+e^-$-colliders for determining anomalous triple gauge couplings (aTGC) at the detector level.
Precise constraints on aTGCs are vital inputs to global SMEFT fits, yet current projections either come from theory-only studies or do not use the full event information.
We fill this gap with an analysis based on a full Geant4 simulation of the ILD detector concept, considering all relevant Standard Model processes, and making optimal use of the full event kinematics.
Our study includes a comparison of various beam-polarisation scenarios and tests the simultaneous determination of systematic uncertainties and additional model parameters.

Speaker: Leonhard Reichenbach (CERN / University of Bonn (DE))

16:30 → 18:00 Superconducting RF Systems

16:30 Recent SRF cavity fabrication studies at KEK

This talk introduces SRF cavity fabrication research at KEK over the past five years. The common objective is to reduce the cost of SRF cavities. The first topic is a Nb/Cu cavity in which the cavity body is made of copper and the inside is coated with niobium to induce superconductivity. The inner surface of the accelerating cavity must be smooth, and a seamless cavity is ideal as a base for the coating. We developed the idea of manufacturing a seamless cavity from a single copper tube and successfully prototyped it by hydroforming. At CERN, we applied a niobium coating with a film thickness of about 5 µm by magnetron sputtering. RF performance tests were conducted at KEK, and the accelerating gradient reached 12 MV/m at 4 K and 16 MV/m at 1.85 K. We are currently working on further improvements to improve performance. After hydroforming, the inner surface of the cell becomes rough. We report our efforts to improve the roughness by polishing. The second topic is the manufacture of niobium SRF cavities by cold spray. Cold spray is a lower-temperature solid-state thermal spray process that deposits metal powder using a heated inert gas through a supersonic nozzle. When the material hits at supersonic speed and reaches the critical speed, the particles themselves are plastically deformed to form a film. We proposed a novel manufacturing method to form a thick niobium film on the surface of a mandrel by cold spray using niobium powder, then remove the mandrel to finish a hollow shape. We confirmed the feasibility of the proposed method for a 3 GHz one-cell cavity. We also carried out an RRR measurement of the cold-sprayed niobium specimen and obtained a value of 11. We report on these results. The third topic is the manufacture of a niobium foil cavity. We proposed a new approach to fabricating the cavity body by spinning a 1.5-mm-thick niobium sheet, and we prototyped a 3 GHz one-cell cavity. To improve the cavity's structural strength after spinning, we deposited a copper layer on the outer surface using cold spray. We report on the details of the manufacturing process.

Speaker: Prof. Masashi YAMANAKA (KEK)

16:50 Development of an organic-solvent electropolishing process for mirror finishing of Nb

Speaker: Dr Takeyoshi Goto (KEK)

17:10 Statistical evaluation of mechanical properties of fine grain niobium sheets.

Tokyo Denkai has supplied over 20000 fine grain (FG) niobium sheets for superconducting cavities for the European XFEL, LCLS-II, LCLS-II HE and SHINE projects. In this study, tensile test data obtained during mass production were statistically evaluated. Tensile strength, 0.2 % proof strength and elongation showed normal distributions. The minimum values estimated as the mean minus three standard deviations were 153 MPa, 48 MPa and 45 %, respectively. According to JIS B 8266, the design-stress strength (allowable stress) of FG niobium was calculated to be 32 MPa based on the 0.2 % proof strength. The differences in tensile strength and 0.2 % proof strength between the rolling and transverse directions were small. On the other hand, elongation showed larger differences, mainly due to the fracture position of the tensile test specimens. In addition, the influence of a change in the final heat-treatment condition was statistically evaluated. The tensile strength and 0.2 % proof strength showed statistically significant changes, but the magnitude of the changes was small compared with the specified values. These results show that statistical evaluation of mass-production data is useful for evaluating the mechanical properties of FG niobium and confirming the validity of manufacturing conditions.

Speaker: Hiroaki Umezawa (Tokyo Denkai Co., Ltd.)

17:30 Improved mid-T heat treatments for cavity performance and the upgrade of DESY’s B-mapping system

Speaker: Dr Marco Voige (DESY)

17:50 Discussion

Speaker: Yasuchika Yamamoto (KEK)

Thursday 12 November

09:00 → 10:30 Plenary: Plenary Thu-1

09:00 SCRF latest technology and for future

Speakers: Hiroshi Sakai (KEK), Hiroshi Sakai (Institute for Solid State Physics, University of Tokyo)

09:25 Status of ATF2

Speakers: Angeles Faus-Golfe (Instituto de Fisica Corpuscular (IFIC) CSIC-UV), Angeles Faus-Golfe (IJClab)

09:50 Progress of Positron source

Speakers: Gudrid Moortgat-Pick (Unknown), Gudrid Moortgat-Pick

10:10 Ghost Collider (ERL)

Speaker: Kaoru Yokoya

10:30 → 11:00 Coffee break

11:00 → 12:30 Beyond Standard Model

11:00 → 12:30 Electron/Positron Sources

11:00 Generation of Polarized Positron Beams for Ce+BAF

The generation of polarized positron beams for the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is based on bremsstrahlung radiation and electron-positron pair production by a 90% longitudinally polarized electron beam in a rotating tungsten target. The required electron beam energy and target thickness for generating a 100 nA positron beam with 60% polarization and a normalized emittance of 100 mm·mrad are calculated. To prevent target overheating and damage, the peak energy deposition density (PEDD) is also calculated. The electron beam current, beam spot size on the target, and target rotation speed are determined for a PEDD limit of 35 J/g for the tungsten target. The objective of this study is to work backward from the CEBAF 6D acceptance to determine the required parameters of the primary electron beam and tungsten target for positron production.

Speaker: Andriy Ushakov (Jefferson Lab)

11:30 Photocathodes, Polarization, and Beyond: Advances in Electron Source Development

GaAs based photocathodes play a crucial role as the primary source of polarized electron beams in various accelerator facilities, including CEBAF at Jefferson National Laboratory and the Electron Ion Collider (EIC) at Brookhaven National Laboratory in the USA. The electron pre-injector at the EIC requires a 1-2 nC bunch with at least 85% spin polarization from a superlattice GaAs photocathode, with longitudinal polarization subsequently rotated to transverse directions using a pair of Wien filters before injecting into the linac. To address the source requirements, we have carried out an extensive study of MOCVD-grown superlattice GaAs/GaAsP structures incorporating a Distributed Bragg Reflector (DBR) underneath. We have incorporated different surface cleaning and activation mechanisms to improve the QE and lifetime of the photocathodes. Besides, 2D protective coatings for polarized electron sources are being explored. In this paper, we will report our advances in electron source development.

Speaker: Jyoti Biswas (Brookhaven National Laboratory)

12:00 Recent advances in long-lifetime photoelectron sources at Jefferson Lab

Highly spin-polarized electron beams for accelerators are almost universally generated by laser-driven, DC-biased photoelectron sources containing GaAs-based photocathodes. These sources are subject to damage mechanisms causing the gradual destruction of the photocathode surface at a rate at least proportional to the beam current, effectively limiting the achievable average current for a given continuous operating time. As the ongoing development of polarized, high-current electron machines and positron conversion targets is pushing the average current requirements beyond what has been reliably demonstrated, Jefferson Lab is pursuing R&D efforts to greatly increase the lifetime of photoelectron sources. Employing a combination of strategies such as deflecting fields for ions, optimized laser profiles, and photocathode materials with enhanced optical absorption, we hope to achieve a tenfold increase in the available average current. In this talk, I will give an overview of the ongoing activities, recent progress made, and the remaining challenges.

Speaker: Max Bruker (Jefferson Lab)

11:00 → 12:30 Flavor, Top and QCD

11:00 Toponium at the ILC revisited

Spin singlet toponium $\eta_t$ has been discovered at the LHC by using di-lepton angular correlation of semileptonically decaying top and anti-top quarks. We study di-lepton distribution from spin triplet toponium states, $\Theta$ and $\chi_t^1$, which are produced in $e^+e^-$ annihilation. We examine asymmetries in the dilepton distributions observable with beam polarization at the ILC.

Speaker: Yajuan Zheng

11:00 → 12:30 Higgs and Electroweak

11:00 Precision Higgs Physics and Higgs Self-Coupling Measurements at the XFEL Compton Collider

The X-ray Free-Electron Laser (XFEL) Compton Collider (XCC) concept
offers a uniquely powerful environment for precision Higgs sector
measurements, providing complementary strengths to proposed $e^+e^-$
and future high-energy hadron colliders. We present comprehensive
physics sensitivity studies for both single Higgs production at
$\sqrt{s} = 125$ GeV and Higgs pair production at
$\sqrt{s} = 280$ and $380$ GeV at the XCC.

Single Higgs Production ($\sqrt{s} = 125$ GeV):
We investigate hadronic, semi-leptonic, and fully leptonic decay
channels of the Higgs boson, including challenging final states such as
$H \to s\bar{s}$. The analysis leverages the sharply peaked
$\gamma\gamma$ luminosity spectrum of the XCC with an advanced set
transformer--based deep learning architecture applied directly to
particle-flow object point clouds to achieve substantially enhanced
sensitivity over traditional $\gamma\gamma$ collider approaches.

Higgs Self-Coupling ($\sqrt{s} = 280$ and $380$ GeV):
We analyze double Higgs production in the
$\gamma\gamma \to HH \to b\bar{b}b\bar{b}$ channel at 380 GeV.
Utilizing an ensemble of boosted decision trees (BDTs) optimized with a
genetic algorithm to separate signal from background, the results
project a precision on the Higgs self-coupling ($\kappa_\lambda$)
between 7\% and 12\%. Initial results from a study of the most
sensitive $\gamma\gamma \to HH$ channels at $\sqrt{s} = 280$ GeV are
also presented.

Together, these results highlight the XCC's capability to probe
electroweak symmetry breaking and single- and multi-Higgs couplings
with extreme precision.

Speaker: Umar Qureshi (Stanford University)

11:18 Study of the H to bs search at the ILC

Flavor-changing Higgs decays are highly suppressed in the Standard Model and provide an important probe of new physics. In particular, the $H \to bs$ decay is a rare flavor changing decay, and the search for this decay provides an important probe of the flavor structure of the Higgs boson. In this study, we investigate the feasibility of searching for the $H \to bs$ decay using simulation data based on the International Large Detector (ILD) concept for the International Linear Collider (ILC). The analysis focuses on the $e^+e^- \to ZH$ process at a center-of-mass energy of 250 GeV, using the $Z \to \ell^+\ell^-$ decay channel.
To effectively separate the $H \to bs$ signal from other Higgs decay backgrounds, we investigate event-selection criteria based on kinematic and flavor-tagging information. In this contribution, the $H \to bs$ search in the $Z \to \ell^+\ell^-$ channel, based on a preliminary event selection using the ILD detector concept, will be presented.

Speaker: Kanako Watanabe

11:36 Probing Extended Higgs Sectors through Zh Production

The discovery of the Higgs boson has opened new avenues to probe physics beyond the Standard Model. Extended Higgs sectors predict additional scalar and pseudoscalar states that can modify Higgs production at the LHC. In this talk, we investigate pseudoscalar contributions to Higgs-strahlung, the associated production of a Higgs and Z boson, within the Two Higgs Doublet Model and its extension with a complex singlet scalar. We study both light and heavy pseudoscalar scenarios and examine their effects on the total and differential production rates. While a light pseudoscalar near 95 GeV has a limited impact on the production rate, heavier pseudoscalars can lead to significant deviations from the Standard Model prediction and constrain otherwise viable regions of parameter space. We discuss the implications of current LHC measurements and the prospects for improved sensitivity with future data.

Speaker: Juhi Dutta

11:54 One-loop corrections to the discovered Higgs boson decays in the real Higgs triplet model

Higgs precision measurements provide an opportunity to test various extended Higgs models. To exploit the high precision of future experimental measurements, theoretical predictions must be calculated with comparable precision by including higher-order corrections. In this talk, we focus on the real Higgs triplet model, a representative extended Higgs model with custodial symmetry violation. We show that characteristic predictions of the model are obtained after including one-loop corrections, allowing the real Higgs triplet model to be distinguished from other simple extended Higgs models. This distinction can be achieved through high-precision measurements of the discovered Higgs boson at future lepton colliders.

Speaker: Kodai Sakurai

12:12 Evaluation of the measurement accuracy of Higgs boson coupling constants via $e^+e^- \to ZH(jj)$ processes at the International Linear Collider

The measurement of Higgs coupling constants is one of the most important goals for Higgs factories. While the couplings of the Higgs boson to the top and bottom quarks have been experimentally confirmed, the coupling to the lighter quark like strange has not yet been observed due to its small decay branching ratio.

We evaluated the measurement accuracy of the Higgs couplings using simulated data based on the ILD detector concept for the International Linear Collider. The analysis focuses on the process $e^+e^- \to Z(\bar{q}q)H$ at a center-of-mass energy of 250 GeV, where we attempt to simultaneously determine the couplings for $H \to b\bar{b}/c\bar{c}/gg/s\bar{s}$ decay modes.To distinguish these processes, we explored two approaches: one primarily utilizing a multi-class deep neural network and the other based on template fitting. In our study, flavor tagging is performed using a Particle Transformer (ParT), which identifies hadrons taking dE/dx and 100 ps time-of-flight as input variables and enables strange tagging. The analysis can be divided into three channels according to Z boson decay modes (neutrino / charged lepton / hadron channel), and we focus on hadron channel in this talk.

Speaker: Takumi Seino (The university of Tokyo)

11:00 → 12:30 Joint: SRF and High Gradient RF

11:00 Recent advances in high-Q/high-gradient at Jefferson Lab

Speaker: Dr Pashupati Dhakal (JLAB)

11:20 Redefining SRF surface roughness that matters for attainable surface magnetic fields

Speaker: Dr Eric Lechner (JLAB)

11:40 Recent results from Nb3Sn R&D at Fermilab

Speaker: Dr Grigory Eremeev (FNAL)

12:00 Recent advances in high-Q/high-gradient at Fermilab

Speaker: Dr Daniel Bafia (FNAL)

12:20 Discussion

Speaker: Yasuchika Yamamoto (KEK)

11:00 → 12:30 Upgrade with Advanced Accelerator Technologies

11:00 Enhancing gamma-gamma collider luminosity through scattering-laser wavelength selection in the presence of prolific electron-positron pair production

A gamma-gamma collider capable of reaching the multi-TeV frontier of particle physics may enable the study of phenomena beyond the Standard Model. Based on compact linear wakefield accelerator technology, such a collider could be realized by Compton scattering multi-TeV lepton beams off moderate-intensity laser pulses close to the collider interaction point, producing the required gamma-photons. It is shown that, for a wide range of scattering-laser wavelengths, gamma-gamma collisions at the interaction point can meet the luminosity requirements for novel particle physics studies, even in the presence of the prolific electron-positron pair production that accompanies the interaction of the scattering laser with the multi-TeV lepton beam. It is shown that an enhancement in gamma-gamma collider luminosity can be achieved for 250 nm and 1.25 nm scattering lasers. These enhanced luminosities need to be compared to that of the electron-positron colliders, which also have a number of important interaction point physics problems. In particular, whether the beamstrahlung, electron-positron pair production, and beam disruption can limit the physics reach of such a collider. It is shown that in the strong beamstrahlung regime the high energy collision luminosity is significantly reduced due to photon emission, making gamma-gamma collider option more attractive. The amount of reduction depends on the beamstrahlung strength, which is controlled by the particle bunch charge, length, emittance, and beta function. The obtained results favor the use of extremely short electron-positron bunches for the future collider design.

Speaker: Stepan Bulanov (Lawrence Berkeley National Laboratory)

11:20 The ReLiC– Recycling Linear Polarized e+e- Collider

I will present our studies of linear collider e+e- collider recycling both the used particles and the beam energy. After each collision particles are decelerated and cooled in damping rings. Recycling collided particles and their energy opens path to very high luminosity O(1036) cm-2 sec-1. ReLiC will be able to collide highly polarized electrons and positrons. The main challenges of such concept are in computing low energy tail caused by beamstrahlung and limiting emittance blow-out during collisions. Beamstrahlung control requires colliding super-flat beams with size ratio exceeding 1,000. I will present progress with simulations of collision effects as function of the c.m. energy and discuss requirements for damping ring in such collider.

Speaker: Vladimir Litvinenko (Stony Brook Univeristy)

11:40 Narrow Band γγ Colliders: From Precision Higgs Factories to the 10 TeV Energy Frontier

Photon-photon (γγ) Compton colliders offer compelling, high-efficiency pathways to explore the fundamental building blocks of matter without the technological bottlenecks associated with high-intensity positron sources and plasma-based positron acceleration. Furthermore, γγ Compton colliders operating in a narrow-band energy configuration can offer, in many circumstances, additional advantages for precision measurements and energy-frontier discovery. This presentation outlines the design concepts, advanced accelerator technologies, and physics capabilities of narrow band γγ colliders spanning precision Higgs factories to 10 TeV in the center-of-mass.

First, we review the conceptual design of the X-ray Free-Electron Laser (XFEL)-based γγ Compton collider (XCC) Higgs factory. Driven by cold copper distributed coupling (C$^3$) accelerator technology, XCC collides 62.8 GeV electron beams with 1 keV XFEL pulses to generate colliding beams of 62.5 GeV photons. The resulting sharply peaked γγ luminosity spectrum produces 75,000 Higgs bosons per 10$^7$ s year, yielding Higgs coupling measurements comparable in precision to $e^+ e^-$ colliders, with an upgrade path to 280 GeV for triple Higgs coupling studies. Issues of beamline layout, the machine-detector interface and backgrounds are addressed.

Extending the narrow-band approach to the 10 TeV frontier, we evaluate a high-geometric-luminosity configuration of a plasma wakefield $e^-e^-$ collider ($L_{e^- e^-}^{geo} =60\times 10^{35} $ cm$^{-2}$ s$^{-1}$) utilizing short-wavelength, 1 keV scattering lasers paired with 5 TeV electron beams. While optical/UV scattering ($\hbar\omega_0=2.5$ eV) leads to severe primary interaction region electromagnetic fields up to $6\times 10^{16}$ V/m that induce heavy beamstrahlung and coherent pair production, the 1 keV laser configuration mitigates these fields by over two orders of magnitude. This yields a clean, highly peaked luminosity spectrum with a partial 1.5% γγ luminosity of $L_{\gamma\gamma}^{1.5\%}=0.33\times 10^{35}$ cm^{-2} s$^{-1}$ and low pileup ($\langle\mu\rangle_{pileup}\approx 3.3$). Together, these designs demonstrate the unique physics and accelerator advantages of X-ray-driven Compton colliders from 125 GeV to 10 TeV.

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

12:00 Proposal of electron-positron ERL collider

Energy recovery linac, ERL is promising scheme for high-luminosity colliders with reasonable construction costs and power supply. A racetrack-type ERL accelerator is proposed as a compact electron -positron collider at the Z-pole. The circumference is approximately 6 km. It is assumed to be located at the Tsukuba campus of KEK.

Speaker: Miho Shimada (KEK)

12:30 → 14:00 Lunch

14:00 → 15:30 Calorimetry + Particle ID

14:00 Construction of a highly compact and finely granulated electromagnetic calorimeter

Highly compact and finely segmented electromagnetic calorimeters are required for applications in the LUXE experiment at DESY and at future electron–positron colliders as luminometers. A small effective Molière radius and high spatial granularity are essential for resolving electromagnetic showers in high-occupancy environments. At collider detectors, such calorimeters precisely define the fiducial volume and need little space.
A silicon–tungsten sampling calorimeter is being developed within the FCAL and DRD Calo collaborations. Its construction poses a significant technological challenge, since the gaps between the tungsten absorber plates must be kept as small as possible in order to preserve the intrinsic compactness of tungsten. The active layers therefore have to integrate the silicon pad sensors, signal routing, high-voltage distribution and mechanical support within a very limited thickness.
The basic active unit is a highly compact silicon sensor plane in which the pad sensor is connected to thin Kapton fan-outs carrying signal and bias lines and embedded in a lightweight mechanical support. The sensors are read out at their edges by dedicated front-end ASICs such as FLAME or FLAXE, providing analogue amplification, digitisation and fast data transmission while keeping the electronics outside the sensitive area. The absorber stack is assembled with precisely manufactured tungsten plates and thin active layers in a mechanically controlled structure designed to maintain small and uniform inter-layer gaps.
The design, assembly and integration procedures developed for these modules are presented, together with experience from the construction of a multi-layer prototype. The completed system has been operated in electron beams at DESY, providing a validation of the mechanical integration, sensor connectivity and full readout chain of this highly compact calorimeter concept.

Speaker: Veta Ghenescu (Institute of Space Science (RO))

14:20 Performance of a compact and finely granulated ECAL in an electron beam of 1 - 6 GeV energy

An ultra-compact sampling electromagnetic calorimeter based on tungsten absorber plates interspersed with thin silicon sensor layers was tested in an electron beam at DESY in June 2025. The thickness of the tungsten plates amounts to 1 radiation length, and are separated by only 1 mm. Data were collected with electron energies ranging from 1 to 6 GeV. The ongoing analysis includes measurements of the transverse shower profile and Moli`ere radius, the position and angular resolution, and the longitudinal development of electromagnetic showers as a function of beam energy. Dedicated data sets are also used to quantify the effects of inactive gaps between adjacent detector towers. Preliminary results from these analyses will be presented.
These studies in a test-beam offer important input for the optimization of highly granular and compact electromagnetic calorimeters for luminometers in future electron-positron collider experiments.

Speaker: Veta Ghenescu (Institute of Space Science (RO))

14:40 Novel algorithms for a compact electromagnetic calorimeter alignement

To match the physics goals of future Higgs factory to secure the required precision of luminosity measurement, luminosity detectors need to be positioned with micrometer precision. 
Last year, prototype of  a highly compact and granular positron calorimeter (ECAL-P) for LUXE experiment was tested at the DESY electron beam. The design of ECAL-P was based on the concept proposed for luminosity calorimeters at future e+e- colliders. For calorimeter alignment, additional silicon sensor layer was placed in front of the calorimeter. An edge-detection procedure based on Hough Transform can be then used to find position of the front sensor pads in the reference frame of the beam telescope. 
A novel alignment algorithm has been developed and implemented for the calorimeter test data analysis. With huge statistics of collected electromagnetic showers not only the calorimeter position with respect to the beam telescope but also the internal structure of the calorimeter can be established with micromicron precision from the dedicated likelihood fit to the data. Accuracy of the algorithm was also verified with the Monte Carlo data from Geant4 simulation of the test setup.

Speaker: Veta Ghenescu (Institute of Space Science (RO))

15:00 Adapting high-granularity silicon calorimeters from Higgs factories to dark-sector experiments: optimization studies for LUXE-NPOD

Highly granular silicon-tungsten calorimeters, originally developed for precision measurements at future Higgs factories, provide excellent spatial sampling of electromagnetic showers together with compact transverse shower development. These features also make them attractive for experiments searching for feebly interacting particles, where the reconstruction and separation of nearby photons can be essential.

In this contribution, we present recent studies of a highly granular SiW calorimeter concept for the LUXE New Physics with Optical Dump (NPOD) proposal. Building on previous proof-of-concept studies, we investigate the interplay between detector geometry and the reconstruction of photon energy, impact position and incident direction. We also explore machine-learning-based reconstruction methods designed to exploit the full three-dimensional information of the calorimeter showers and compare their performance with conventional reconstruction techniques. These studies provide a framework for the joint optimization of detector geometry and reconstruction algorithms for compact calorimeters in dark-sector experiments.

Speaker: Adrian Irles (IFIC, CSIC-UV)

14:00 → 15:30 Electron/Positron Sources

14:00 FCC-ee positron source design at 3 GHz

A high-performance positron source is essential for FCC-ee to provide the high-intensity, low-emittance beams required for rapid injection, especially in the Z-pole operation mode. In the FCC-ee Feasibility Study, the reference positron source is based on a 2.86 GeV electron drive beam impinging on a 15 mm tungsten target, followed by an HTS matching device and a 2 GHz travelling-wave RF capture section embedded in a 0.5 T solenoidal channel. A chicane separates electrons from positrons, after which the positron linac, based on the same 2 GHz RF structures as the capture section, is divided into two focusing sections: a solenoid-focused section with a 0.5 T field, followed by a FODO-based section with quadrupole focusing between the RF structures.
This work investigates 3 GHz S-band RF structures as potential alternatives for the FCC-ee positron linacs, motivated by the maturity and broad availability of high-power S-band RF technology. Two 3 GHz configurations are studied in detail. The first, denoted v1, employs five 3 m long travelling-wave structures in the capture section, whereas the second, v2, uses twelve 1.2 m standing-wave structures developed for the P³ experiment. In both configurations, the capture structures are embedded in a solenoidal focusing channel. Following electron–positron separation in a chicane, the positron beam is matched into a quadrupole-focused linac based on large-aperture 3 GHz travelling-wave structures. Its first and second sections contain 16 and 48 structures, respectively. A downstream energy-compression system, comprising a magnetic chicane and four additional travelling-wave structures, together with a matching line, prepares the beam for injection into the damping ring. A 6D DR acceptance approach, benchmarked against direct particle tracking through the damping ring, is incorporated into the fast optimization workflow. Start-to-end simulations are performed using RF-Track, while the princpal machine parameters are optimized with Xopt. By retaining a common downstream layout, the study enables a consistent comparison of the two capture configurations, identifies their principal performance trade-offs and provides the basis for establishing the current 3 GHz baseline design for the FCC-ee positron source.

Speaker: Yuting WANG (IJCLab - IN2P3/CNRS)

14:30 Status of P3 Experiment

The PSI Positron Production (P3, or P-cubed) experiment is a demonstrator of a positron source and capture system developed within the FCC-ee injector study. Installed at the SwissFEL facility of the Paul Scherrer Institute, the experiment aims to significantly increase the positron yield compared with the current state-of-the-art. The facility combines a conventional pair-production target with an advanced capture system based on high-temperature superconducting solenoids and large-aperture RF cavities to maximize positron collection efficiency. Following the successful installation of the experimental setup, this presentation reports the first e⁺ beam measurements, representing an important milestone for the P-cubed experiment and for the development of high-intensity positron sources for future electron-positron colliders.

Speaker: Simone Giroldi (PSI and EPFL)

15:00 Positron Source for HALHF and Future Collider Designs

The current polarized source for the HALHF design has been studied and synergies with positron sources for ILC, LC and CLIC will be discussed.

Speaker: Gudrid Moortgat-Pick

14:00 → 15:30 Joint: Higgs/EW and BSM

14:00 FOEWPT in the RxSM: LC opportunities

We analyze the SM extended by a real Higgs singlet, RxSM, in the parameter space that yields a First Order Electroweak Phase Transistion (FOEWPT, one of the requirements to explain the baryon asymmetry of the universe via electroweak baryogenesis). We demonstrate the physics opportunities for future high-energy e+e- colliders in such a scenario. In particular, we emphasis the complementarity between collider probes and measurements of the corresponding gravitational waves at LISA.

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

14:18 BSM triple Higgs coupling determination with Neural Networks

We use a Neural Network (NN) to determine the size of a BSM triple Higgs coupling, $\lambda_{hhH}$, where $h$ is the Higgs boson discovered at the LHC, and $H$ is a heavier CP-even Higgs boson. The underlying model is the SM extended by a real singlet (RxSM). Using the processes $e^+e^- \to Zhh$ and $e^+e^- \to \nu\bar\nu hh$, we feed the anticipated $m_{hh}$ invariant mass distributions into the NN to determine the value of $\lambda_{hhH}$. We find that this method is superior to traditional approaches.

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

14:36 Enhanced CP Sensitivity in Higgs di-tau decays with Energy Correlators at Higgs factories

The generic azimuthal angle difference between the decay planes of tau leptons are a powerful probe of CP violation in Higgs decays through tau polarisation. In the $\tau^\pm\to\rho^\pm\nu$ channel, the spin-analysing power is suppressed by the mixture of longitudinal and transverse $\rho$ polarisations, limiting the sensitivity. We propose an energy correlator-inspired method that enhances the contribution of the longitudinal $\rho$ component, thereby increasing the effective analysing power from $\alpha_\rho \approx 0.45$ to values close to unity. For $h\to\rho^+\rho^-\nu\bar\nu$, the CP-odd modulation amplitude in the neutrino azimuthal difference grows by a factor $\sim 3.6$, recovering sensitivity comparable to the $\tau\to\pi\nu$ channel. This enhancement significantly improves the sensitivity to CP violation in Higgs di-tau decays, strengthening the reach of future lepton colliders in probing CP-violating tau Yukawa interactions relevant to electroweak baryogenesis. The same energy correlator method applied to $e^+e^-\to Z\to\tau^+\tau^-$ enhances the sensitivity to the $\tau$ polarisation asymmetry $P_\tau \approx 2(1-4\sin^2\theta_W)$, offering improved precision in the determination of $\sin^2\theta_W$. We also quantify the expected experimental reach at future lepton colliders with a full Monte Carlo study including detector simulation.

Speaker: Anjan Kumar Barik (Tsung-Dao Lee Institute School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200120, China)

14:54 Neutrino mass, dark matter, and baryon asymmetry in a three-loop radiative seesaw model and its collider phenomenology

The Standard Model successfully describes particle physics but cannot explain neutrino oscillations, the baryon asymmetry of the universe (BAU), and dark matter. The Aoki-Kanemura-Seto (AKS) model is a new physics model that can explain these three phenomena simultaneously at TeV scale testable by future experiments. However, in the original model published in 2009, the baryon number was not evaluated. In the present work [Enomoto, Kanemura, Taniguchi, JHEP06(2025)036], we introduced CP violation to the original AKS model for evaluating the baryon number and found a benchmark scenario to avoid the current constraint on the electron electric dipole moment while keeping a large enough CP-violating phase for electroweak baryogenesis. In this talk, we evaluate the baryon number in this model with some extension. Furthermore, we present benchmark points that can simultaneously explain neutrino masses, dark matter, and BAU, under various experimental and theoretical constraints. We also discuss prospects for testing the model at future experiments. We investigate gravitational-wave signals from the strong first-order electroweak phase transition and their detectability at future space-based observatories such as DECIGO. At colliders, the new particles predicted by the AKS model, including $S^\pm$ and the additional Higgs bosons $H_2$ and $H_3$, could be directly produced at the High-Luminosity LHC and future electron-positron colliders. Moreover, the sizable non-decoupling effects of the additional scalars required for a strong first-order electroweak phase transition can induce a measurable deviation in the Higgs triple coupling. Collider experiments therefore provide particularly important probes of this model through both direct searches and precision measurements of the Higgs sector.

Speaker: 宙 谷口 (大阪大学)

14:00 → 15:30 Joint: SRF and High Gradient RF

14:00 → 15:30 Upgrade with Advanced Accelerator Technologies

14:00 HALHF: recent progress and relevance toward 10 TeV

The hybrid, asymmetric, linear Higgs factory (HALHF) is a plasma-based collider concept that combines plasma-wakefield acceleration (PWFA) of electrons and radio-frequency (RF) acceleration of positrons for asymmetric-energy collisions at 250 to 550 GeV. This has the potential to overcome the positron problem in PWFA, and provide a cost-effective collider with a reduced footprint. We report on recent progress in the HALHF project as we move toward a pre-CDR. This includes work on emittance preservation in the multistage plasma accelerator, handling of high heat flux and plasma temperatures, the driver-delivery complex, the beam-delivery system, and more. Finally, we discuss how developments in HALHF can be relevant to a 10-TeV collider design.

Speaker: Carl Andreas Lindstrom

14:20 Simulating the Luminosity Spectrum at HALHF

HALHF is a proposed hybrid linear collider with highly asymmetric beam energies. WarpX, a Particle-In-Cell (PIC) code capable of self-consistently simulating beam-beam effects, including beamstrahlung, has been used to characterise the luminosity spectrum expected at HALHF for three different baseline designs with centre of mass energies of 250 GeV, 380 GeV and 550 GeV. The resulting luminosity spectra are compared with independent simulations performed using GUINEA-PIG, a dedicated beam-beam interaction simulation code widely used for linear collider studies. We present the luminosity distributions obtained with both simulation approaches and demonstrate good agreement between them.

Speaker: Lucy Bishop (DESY)

14:40 Plasma-based Linear Colliders: Relevant Experimental Demonstrations at FLASHForward

Plasma-based accelerators can produce accelerating fields several orders of magnitude stronger than those of conventional accelerators. They operate by driving density waves in a plasma using compact particle beams or laser pulses. The resulting strong wakefields are then used to accelerate a trailing electron bunch. The FLASHForward experiment at DESY performs fundamental research on this scheme using FEL-quality bunches from the FLASH linear accelerator. This contribution will summarise recent results from FLASHForward to provide insight into the state of beam-driven plasma accelerator research.

The trailing bunch can be injected internally from the plasma, a promising route to ultra-low emittance. Results from FLASHForward will be presented demonstrating reproducible density down-ramp injection and GV/m acceleration of bunches with collider-relevant quality.

Both matching into plasma-based accelerating stages and collider final-focusing systems require strong focusing fields. Fields of the required magnitude can be produced by passive plasma lenses. Experimental results will be discussed showing that such lenses can preserve FEL-quality transverse slice emittance and produce focusing fields two orders of magnitude stronger than permanent quadrupole magnets.

A novel diagnostic of the driver-to-witness energy-transfer efficiency will also be shown. Exploiting the emitted plasma light, the technique is parasitic and longitudinally resolved.

Finally, preliminary experimental results, including plasma acceleration, will be presented on generating twin bunches at the photocathode suitable for plasma wakefield acceleration with tunable delay and bunch shapes.

Speaker: Marcel Hohmann (DESY)

15:30 → 16:00 Coffee break

16:00 → 17:30 Calorimetry + Particle ID

16:00 Beam Test of the SiW-ECAL "Uniform Prototype" Results and Perspectives

The Silicon-Tungsten Electromagnetic Calorimeter (SiW-ECAL), is one of the key sub-detector for the ILD Detector Concept and is being investigated as a component of future fixed target experiments looking for Dark Photons (EBES, LUXE, SHiP, Lohengrin).
After many iterations and tests, an ultimate version of the front-end boards based on SKIROC2 ASICs from the Omega lab, and a new assembly procedures have been devised.
In June 2026, after a meticulous preparation, an almost uniform prototype of the SiW-ECAL with 15 layers was built and tested at the CERN SPS. While the data is still being analysed, early results suggest good noise and high-energy electrons performances.
These early results and perspectives for experiments will be presented.

Speaker: Vincent Boudry (Laboratoire Leprince-Ringuet, CNRS/IN2P3, École polytechnique)

16:20 Performance Evaluation of the 15-Layer SiW-ECAL Technological Prototype with CERN SPS Beam Test Data

Precision measurements of the Higgs boson and electroweak interactions at future $e^+e^-$ collider experiments, such as the ILC, CLIC, and FCC-ee, are crucial for exploring new physics. Achieving this requires a high-granularity electromagnetic calorimeter, for which the silicon-tungsten electromagnetic calorimeter (SiW-ECAL) is one of leading candidates. While previous physics prototypes validated the fundamental concept, demonstrating the performance of a technological prototype designed under realistic mechanical and electronic constraints remains a key milestone. This study focuses on the analysis of beam test data collected in June 2026 at the CERN SPS, utilizing a 15-layer SiW-ECAL technological prototype developed for future Higgs factories. In this presentation, we present the results of calibration and energy reconstruction.

Speaker: Taiki Kamiyama (University of Tokyo)

16:40 5D-Calorimetry - Recent Results from the Calo5D Project

One current focus of calorimeter reconstruction algorithm development has been the utilisation of time information as the fifth dimension of calorimeter data.
In this talk, recent work of the CALO5D team is presented, studying the role of timing in highly granular CALICE-type calorimeters. The studies focus on the calorimeter concept as implemented in the International Large Detector (ILD) concept proposed for the ILC and FCC-ee.

The talk will cover the ongoing re-optimisation of the ILD electromagnetic calorimeter (ECal), including the interplay between detector design, timing performance and reconstruction. Particular emphasis will be placed on machine-learning-based reconstruction approaches and their performance compared with established particle-flow (PFlow) reconstruction such as Pandora and APRIL. These approaches are investigated across different levels of complexity, ranging from the optimisation of specific observables, such as the electromagnetic energy fraction f_em, to fully end-to-end reconstruction of calorimeter data. Their impact on jet energy resolution and other relevant reconstruction observables will be discussed.

In addition, the implications of operating such a highly granular calorimeter at the FCC-ee are considered. In particular, studies of the expected data rates and power consumption will be presented, addressing the challenges posed by the large volume of highly granular, time-resolved calorimeter data and their implications for the design and operation of a future detector. Finally, the implementation of the CALICE-type calorimeter in the simulation framework of the SHiP experiment and its possible impact on the detector performance are presented.

Speakers: Roman Poeschl (Université Paris-Saclay (FR)), Ulrich Einhaus (KIT), Vincent Boudry (Laboratoire Leprince-Ringuet, CNRS/IN2P3, École polytechnique)

16:00 → 17:30 Electron/Positron Sources

16:00 Results of Active Plasma Lens and Pulsed Solenoid Studies as Optical Matching Devices at the ILC Polarized Positron Source

The polarized positron source of the International Linear Collider requires efficient optical matching of the highly divergent positron beam produced at the target.
The long ILC bunch train also places strong requirements on the stability and operation of the matching device.
This contribution will summarize studies of two alternative concepts: a pulsed solenoid and an active plasma lens.

A pulsed solenoid was studied using numerical optimization and magnetic-field measurements. A simulation framework coupling COMSOL and
ASTRA was used to optimize the solenoid geometry and study positron capture. The simulations identified a transverse dipole kick as an important limitation of the current design,
while measurements of a prototype showed promising temporal field stability.

As a novel alternative, a downscaled active plasma lens prototype was experimentally studied with a focus on discharge stability and long-term operation.
The measurements showed significant electrode erosion and material deposition, changes in discharge behavior over time
and limitations for repetitive MHz operation. High-speed imaging was used to further investigate the spatial and temporal behavior of the plasma discharge.

The results provide a comparison of both concepts and identify the main challenges for their application at the ILC.

Speaker: Niclas Hamann (Uni Hamburg/DESY Hamburg)

16:00 → 17:30 Higgs and Electroweak

16:00 Event Reconstruction and Higgs-to-Invisible Analysis with ILD Detector Models for FCC-ee

The International Large Detector (ILD) concept is being studied as a possible detector option for several future $e^+e^-$ Higgs factories. To assess the physics potential of ILD-like detector configurations at FCC-ee, the existing detector models and reconstruction chain are being adapted to the relevant FCC-ee beam conditions, event environment, and software framework. This contribution presents the recent progress of event reconstruction, with particular emphasis on charged-particle tracking. The performance of the adapted models is evaluated using tracking efficiency, fake-track rates and momentum resolution. The talk will also report the status of a Higgs-boson decay analysis in which the Higgs boson decays to invisible final states. This channel provides a sensitive probe of physics beyond the Standard Model and places demanding requirements on recoil reconstruction, flavour tagging, missing momentum, and control of detector-induced backgrounds. The analysis is being re-established with the adapted ILD@FCC-ee detector models, providing an integrated test of the reconstruction chain from simulated detector response to physics observables. Recent validation results, remaining challenges, and the prospects for improving the sensitivity of the Higgs-to-invisible measurement, including a comparison with ILD@ILC, will be discussed.

Speaker: Victor Schwan (Deutsches Elektronen-Synchrotron (DE))

16:18 Higgs Precision Calculations and New Developments toward Version 4

H-COUP is a computational tool for evaluating Higgs-boson decay rates and branching ratios, including one-loop corrections, in various extended Higgs sectors. Such precision calculations are essential for interpreting future measurements at Higgs factories, such as the ILC, FCC-ee, and CEPC, and for probing the underlying structure of the Higgs sector.
In this talk, we present the main features of H-COUP and discuss ongoing developments toward Version 4.

Speaker: Kei Yagyu (Tokyo University of Science)

16:36 The Whizard Monte Carlo generator

We present a status report on recent developments in the WHIZARD event generator, an efficient and widely used tool for the simulation of exclusive and inclusive multi-particle processes at lepton colliders. In particular, we review progress in NLO calculations within the Standard Model and beyond, and new developments within the framework of collinear factorization, the Equivalent Vector Boson Approximation and electroweak parton distribution functions. Finally, we outline ongoing work and future plans, such as improvements in exclusive studies of top-quark pair production at the threshold.

Speaker: Wolfgang Kilian (University of Siegen)

16:54 Quark Electroweak Couplings at Future e+e- Colliders

Precision measurements of Standard Model parameters are essential to overconstrain the theory and search for signatures of new physics. These parameters also serve as critical inputs for a wide range of precision physics analyses. In particular, the electroweak couplings of quarks provide valuable insights into the SM gauge structure and enable stringent tests of flavour universality.

In this contribution, we present a prospective study on constraining quark electroweak couplings at future $e^+e^-$ colliders. We discuss how combining measurements across different centre-of-mass energies, both with and without beam polarisation, allows one to disentangle the left- and right-handed coupling components and substantially improve precision beyond the LEP legacy.

Speaker: Krzysztof Mekala

17:12 The bottom quark mass at high scale

Measurements at electron-positron colliders can probe the scale evolution of quark masses predicted by the Standard Model in several ways. LEP and SLD extracted $m_b(m_Z)$ from three jet rates in $Z\rightarrow b\bar{b}$ decay. A future $Z$-pole run can improve the precision considerably, while a measurement of $m_b$ at higher scale is possible from $e^+e^- \rightarrow b\bar{b}$ production at 250 GeV and above. A very precise determination of $m_b(m_H)$, with an uncertainty of 10s of MeV, can be achieved from measurements of Higgs decay rates in the Higgs factory runs at $\sqrt{s}$ = 250 GeV and 550 GeV.
In this contribution, we present the state-of-the-art extraction of $m_b(m_H)$ at the LHC, which is measured by the ATLAS experiment to be $2.73^{+0.27}_{-0.25}$ GeV, and provide updated projections for the HL-LHC and future colliders. We also present a proposal for an alternative methodology, where $m_b(m_H)$ and the bottom-quark Yukawa coupling are extracted simultaneously to provide a more model-independent result, as well as projections for the sensitivity of such extraction in a future electron-positron collider.

Speaker: Juan Ramírez Alfaro (IFIC (UV/CSIC))

16:00 → 17:30 Upgrade with Advanced Accelerator Technologies

16:00 The Linear Ghost Collider - Efficient & High Luminosity LC Upgrade

A 550 GeV centre-of-mass Higgs factory is presented, the Linear Ghost Collider (LGC). Acceleration and deceleration is performed within an SRF linac where the bunches transported are net neutral, termed ghost bunches. Within these, one charge partner accelerates, and the other decelerates. In this way energy is recovered after collision, and all particles recycled. An accompanying plenary talk - Ghost Collider (GC) - introduces this concept. LGC comprises an improved configuration to GC that eliminates turn-around arcs. This enables a large reduction in energy lost to synchrotron radiation, and an increase in luminosity as bunches are degraded less, in comparison to GC. Lacking arcs, LGC can therefore be considered as a luminosity upgrade of a pre-built LC. The key innovation is that within a ghost bunch only the velocities of the charge partners must match, not their energies. Therefore, only one charge partner need be accelerated to collision energy. This allows the linac to be split into stages, with the other charge partners only accelerated to collision energy divided by the number of stages - these are termed drive bunches. Recirculation is only needed for drive, not colliding, bunches. As with GC, collisions are arranged between net neutral bunches, this strategy of charge compensation of beamsstrahlung with small disruption allows the energy recovery and re-use of spent colliding bunches. Two variants of LGC are presented: firstly, a pulsed version analogous to GC realisable with existing SRF technology and capable of $34.6\times 10^{34}$ cm$^{-2}$ s$^{-1}$ @ <100 MW electrical power for RF with disruption parameter 2.25; and secondly, a continuous-wave (CW) version based on expected parameters for thin-film $\textrm{Nb}_3\textrm{Sn}$ on copper SRF technology, capable of $348\times 10^{34}$ cm$^{-2}$ s$^{-1}$ @ 160 MW electrical power for RF with disruption parameter 1.48. We compare these values to established collider proposals, and scale to $380$~GeV and $250$~GeV centre-of-mass energies, showing their attractiveness over a large parameter range.

Speaker: Peter Williams

16:20 New Concept: Gravity-Aligned Vertical Electron-Positron Linear Collider

A gravity-aligned vertical electron-positron linear collider is proposed as a concept to break the cost-and-scale impasse that confronts conventional horizontal Higgs factories [KEK Preprint 2026-16, arXiv:2607.24179]. The accelerating axis is oriented along the local gravitational field inside a single deep vertical shaft with a depth of ~3 km. Positrons are injected downward from the surface while electrons are accelerated upward from the bottom, the two beams meeting at an interaction point located deep underground. Targeting a staged center-of-mass energy in the Higgs factory range (250 - 500 GeV), this concept assumes high-gradient, high-efficiency, normal-conducting accelerating structures operated at cryogenic temperature together with a two-beam power-delivery scheme. It can be designed to reuse the existing KEK/SuperKEKB accelerator complex in the KEK Tsukuba Campus. We discuss the advantages of the vertical orientation, namely a small surface footprint, intrinsic azimuthal symmetry of the gravity load, deep vibration isolation of the collision point, a natural vertical alignment reference, a cosmically quiet deep interaction point, a unique opportunity and value in social/industrial evaluation, as well as the principal disadvantages and challenges, including the required high accelerating gradient and the construction of a kilometers-deep shaft. This presentation is deliberately concept-level and is intended to motivate technological innovation and feasibility studies.

Speaker: Abe Tetsuo (KEK)

16:40 Driver guiding and length matching for improved misalignment tolerances plasma accelerators

Plasma wakefield acceleration offers a pathway to compact linacs, but stringent angular tolerances and transverse instabilities pose significant challenges. This paper presents a combined approach of active drive beam guiding and stage betatron length matching to mitigate these effects. Using analytical modelling and PIC simulations based on the HALHF baseline parameters, a reduction of the multi-shot normalised emittance by 3--4 orders of magnitude compared to when no corrections are applied, is shown.

Speaker: Erik Adli (University of Oslo (NO))

17:00 Monoenergetic, stable, electron beam generation via laser wakefield acceleration

The advent of high-peak-power laser technology [1] has enabled compact charged-particle acceleration with a higher acceleration gradient than conventional RF accelerators. One of the most promising schemes is laser wakefield acceleration of electrons [2], and significant progress has been made in achieving 10 GeV energy [3], a few-fs pulse duration [4], a transverse emittance of <1 mm-mrad [5], etc. However, these record values are not simultaneously achieved (or measured), and the parameter stability is not comparable to that of state-of-the-art linear accelerators.
Recently, we developed two schemes that improve both quality and stability. With these schemes, we demonstrated a high-quality electron beam with an energy of 376±16 MeV, a relative energy spread of 1.5±0.5%, a charge of 25.3±7.4 pC, a divergence of 0.5 mrad, and a pointing stability of 0.41ｘ0.23 $\mu$rad (error bars show standard deviations over multiple shots). With the improved quality, free-electron lasing around 20-50 nm was observed using a 2-m-long undulator with the undulator parameter of $K$=0.4-1.4 [6].
These stable electron beams further improved the system; more recently, we have removed some thermal effects, and electron-beam stability has improved [7].
In addition, we discuss the perspective of LWFA for higher electron energy and more stable electron-beam generation.

Acknowledgement
This work was supported by JST-Mirai Program Grant Number JPMJMI17A1, Japan.

References
[1] D. Strickland and G. Mourou, Opt. Commun. 56, 219 (1985).
[2] T. Tajima and J. M. Dawson, Phys. Rev. Lett. 43, 267 (1979).
[3] C. Aniculaesei et al., Matter Radiat. Extremes 9, 014001 (2024); E. Rockafellow et al., Phys. Plasmas 32, 053102 (2025).
[4] O. Lundh et al., Nat. Phys. 7, 219 (2011).
[5] S. K. Barber et al., Phys. Rev. Lett. 119,104801 (2017).
[6] Z. Jin, M. Kando et al., Phys. Rev. Res. 8, 013207 (2026).
[7] Z. Jin et al., Phys. Rev. Res. (submitted).

Speaker: Masaki Kando (Kansai Instiute for Photon Science, Naitonal Institutes for Quantum Science and Technology)

19:00 → 21:00 Banquet

Friday 13 November

09:00 → 10:30 Plenary: Plenary Fri-1

09:00 Summary of physics

09:20 Summary of Detector & software

Speaker: Manqi RUAN (IHEP-LLR/CERN)

09:40 Summary of Accelerator (basic)

10:00 Summary of Accelerator (upgrade)

10:20 Summary of beyond collider

Speaker: Ivo Schulthess (Deutsches Elektronen-Synchrotron (DE))

10:30 → 11:00 Coffee break

11:00 → 13:00 Plenary

11:00 Quantum Information and Future Linear Colliders

Speakers: Kun Cheng, Kun Cheng

11:45 The future of Linear Colliders

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

12:30 Next (next) LCWS

12:35 Farewell

Speakers: Hiroshi Sakai (KEK), Takeshi Dohmae

13:00 → 14:00 Lunch

14:00 → 17:00 Lab tour

14:00 → 17:30 Satellite