Lepton-Photon 2025

25 Aug 2025, 08:00 → 29 Aug 2025, 21:00 US/Central

Monona Convention Center (Madison, WI)

Sridhara Dasu (University of Wisconsin Madison (US))

32nd International Symposium on Lepton Photon Interactions at High Energies

To be held at the Frank Lloyd Wright designed Monona Terrace Convention Center in the heart of Madison, Wisconsin, USA.

For Registration, Visas, etc., please access: Conference Home

Abstracts for Talks is now closed.

To Submit an Abstract for a Poster, please access: Posters

The LP-2025 symposium will feature a broad range of topics of interest to the particle physics, cosmology and particle astro-physics communities. Presentations will include latest experimental results from current experiments, R&D towards future facilities and theoretical developments. There will be plenary talks providing summaries of the state of the field, typically in the morning, detailed reports in the parallel talks and topical results in poster sessions.

Monday 25 August

AM Plenary: Opening Session

10:30 Morning Break

AM Parallel: Accelerator Technologies 1

1 A path towards at 10 TeV Muon Collider

Muons are elementary particles and all their energy is available in a collision, with far cleaner events relative to those produced by the smash of a composite particle like the proton. Muons are also heavy, meaning that they are less prone to synchrotron radiation that effectively limits the energies of circular electron-positron colliders. This raises the prospect that a Muon Collider could exceed the direct energy reach of the Large Hadron Collider, while achieving unprecedented precision measurements of Standard Model processes. In this article we summarize the work and progress achieved so far towards such a machine. We also identify a set of further studies needed and describe a plan to bring these ideas to maturity so that to make a Muon Collider a reality on the timescale of approximately two decades.

Speaker: Diktys Stratakis

2 The 10 TeV Wakefield Collider Design Study

The 10 TeV Wakefield Collider Design Study responds to the P5 Report's call for the ``delivery of an end-to-end design concept, including cost scales, with self-consistent parameters throughout." The Design Study leverages recent experimental and theoretical progress that are the result of a vigorous R\&D program. Wakefield Accelerators provide ultra-high accelerating gradients which enables an upgrade path to extend the reach of Linear Collider Higgs Factories from the electroweak scale to the energy frontier. Here, we describe the organization of the Design Study including timeline and deliverables, and we detail the requirements and challenges on the path to a 10 TeV Wakefield Collider.

Speaker: Spencer Gessner

3 The Cool Copper Collider: An Advanced Concept for a Future e+e- Higgs Factory

A lepton-collider Higgs factory, to precisely measure the couplings of the Higgs boson to other particles, followed by a higher energy run to measure the Higgs self-coupling, is widely recognized as a primary focus of modern particle physics. In this talk, we will present the study of a new concept for a high gradient, high power accelerator with beam characteristics suitable to study the Higgs boson, the Cool Copper Collider (C3), with the goal of minimizing the capital and operating costs. C3 is based on the latest advances in rf accelerator technology and utilizes optimized cavity geometries, novel rf distribution, and operation at cryogenic temperatures to allow the linear accelerator to achieve high accelerating gradients while maintaining the overall system efficiency. We will present the latest demonstrated performance of prototype accelerators and highlight the future development path for C3.

Speaker: Emilio Nanni

4 Recent Progress on Cold Copper Technology

Cold copper accelerating technology represents one of the new frontiers in normal-conducting RF research. It has enabled accelerating structures to reach record high accelerating gradients while providing overall better efficiency. In this talk we will present the latest results on cold-copper high gradient R&D activities including recent results on single-cell and meter-scale structure testing. On going work developing the integrated cryomodules for supporting and aligning structures in linear accelerators will also be presented. Efforts to utilize cold-copper technology for injectors and future colliders will also be summarized.

Speaker: Ankur Dhar (SLAC National Accelerator Lab)

5 Precise luminosity measurement at CMS

Precise luminosity measurement at CMS

Speaker: Niki Saoulidou (National and Kapodistrian University of Athens (GR))

AM Parallel: Charged Lepton Flavor Violation 1

6 The Mu2e experiment: Overview and current status

The Mu2e experiment is a charged lepton flavor violation experiment located at Fermilab, and will search for neutrinoless muon-to-electron conversion in the presence of an aluminum nuclear field. If found, muon-to-electron conversion would unequivocally become evidence of new physics beyond the Standard Model. Mu2e aims to constrain the current signal experimental limits by four orders of magnitude. This presentation will provide an overview of the Mu2e experiment as well as a report of the current status, including the completion of the detector construction prior to the first experimental run, scheduled for 2027.

Speaker: Gonzalo Diaz (Fermi National Accelerator Laboratory)

7 LFV decays of bosons at CMS

LFV decays of bosons at CMS

Speaker: Niki Saoulidou (National and Kapodistrian University of Athens (GR))

8 Charged lepton flavor violation searches at BESIII

The charged Lepton Flavor Violation (cLFV) process is forbidden in the Standard
Model (SM). Even considering the finite but tiny neutrino masses, the cLFV process
is highly suppressed. In this talk, we present the cLFV searches at the BESIII
experiment. The cLFV processes $J/\psi \to e \mu$ and $J/\psi \to e \tau$ have been
searched for with 10 billion $J/\psi$ events collected by BESIII, setting an upper
limits at the level of $10^{-9} - 10^{-8}$, which improve the previously published limits
by two orders of magnitude. In addition, a recent result of search for $\psi(3686) \to e \tau$ will also be presented. These results will be the most stringent upper limits on heavy quarkonium cLFV decays.

Speaker: Fabrizio Bianchi

9 Search for the Lepton Flavour Violating decays $\Upsilon(2{\mathrm{S}}) \to e^{\pm}\mu^{\mp}$ and $\Upsilon(3{\mathrm{S}}) \to e^{\pm}\mu^{\mp}$

Charged lepton flavour violating processes are unobservable in the standard model, but they are predicted to be enhanced in several new physics extensions. We present the results of a search for $\Upsilon(2{\mathrm{S}})$ and $\Upsilon(3{\mathrm{S}})$ decays to $e^{\pm}\mu^{\mp}$ decays.
The search was conducted using data samples consisting of 99 million $\Upsilon(2{\mathrm{S}})$ and 122 million $\Upsilon(3{\mathrm{S}})$ mesons, collected at center-of-mass energies of 10.23 and 10.36~GeV, respectively, by the BABAR detector at the SLAC PEP-II $e^+e^-$ collider

Speaker: Fabio Anulli (Sapienza Universita e INFN, Roma I (IT))

10 Probing Lepton Flavor Violation at Future Electron-Positron Colliders

The production of τμ pairs in electron-positron collisions offers a powerful probe of lepton flavor violation. In this work, we calculate the e+e−→τμ cross section within the framework of the Standard Model Effective Field Theory, allowing for arbitrary e+e− beam polarizations. We then estimate the sensitivities of proposed future linear colliders, ILC and CLIC, to effective lepton flavor-violating interactions. The high center-of-mass energies achievable at these machines provide particularly strong sensitivity to four-fermion operators. Furthermore, the polarization of the e+e− beams enables novel tests of the chirality structure of these interactions. We find that our projected sensitivities not only complement but in certain scenarios surpass those achievable with low-energy tau decay measurements at Belle~II.

Speaker: Pankaj Munbodh (University of California Santa Cruz)

AM Parallel: Dark Sectors (Direct/Indirect) 1

AM Parallel: Heavy BSM Searches at Colliders 1

AM Parallel: Neutrino Physics 1

AM Parallel: Theory 1

11 Thermal corrections to dark matter annihilation cross sections

Infra-red corrections are known to be more acute in thermal field theories than at zero temperature. We use the generalised approach of Grammer and Yennie to show that the cancellation of IR divergences occurs, as in the case of zero temperature field theory, between real and virtual contributions to the cross section, order by order, to all orders in perturbation theory. We use this technique to calculate the NLO thermal cross sections to dark matter annhilation cross sections in a simple manner. While computing the ${\cal{O}(T^2)$ corrections at NLO, we find that the soft IR divergences cancel straightforwardly, but the case of the collinear divergences is more subtle.

Speaker: D Indumathi (The Institute of Mathematical Sciences, Chennai)

12 A theory of quark and lepton compositeness

Are the electron, the neutrinos or the quarks elementary particles, or do they have some substructure? Particle physics experiments have shown that if such substructure exists, its scale must be smaller than about 10^{-18} cm. I will present a theoretical model in which the leptons and the quarks are bound states of a new strongly-coupled interaction, and then I will discuss some tests of the model in future experiments.

Speaker: Bogdan Dobrescu

13 Towards AI-assisted Neutrino Flavor Theory Design

Particle physics theories, such as those which explain neutrino flavor mixing, arise from a vast landscape of model-building possibilities. A model's construction typically relies on the intuition of theorists. It also requires considerable effort to identify appropriate symmetry groups, assign field representations, and extract predictions for comparison with experimental data. In this talk, I will discuss a new strategy ro construct a model. We developed an Autonomous Model Builder (AMBer), a framework in which a reinforcement learning agent interacts with a streamlined physics software pipeline to search these spaces efficiently. AMBer selects symmetry groups, particle content, and group representation assignments to construct viable models while minimizing the number of free parameters introduced. We validate our approach in well-studied regions of theory space and extend the exploration to a novel, previously unexamined symmetry group. While demonstrated in the context of neutrino flavor theories, this approach of reinforcement learning with physics software feedback may be extended to other theoretical model-building problems in the future.

Speaker: Max Fieg (University of California Irvine (US))

14 On-shell recursion relation for massive higher-spin Compton amplitudes

We recursively construct tree-level electromagnetic and gravitational Compton amplitudes of higher-spin massive particles by the all-line transverse momentum shift. With three-point amplitude as input, we demonstrate that higher-point electromagnetic and gravitational Compton amplitudes are on-shell constructible up to spin $s = 3/2$ and $s = 5/2$, respectively, under the all-line transverse shift after imposing the current constraint condition. We unambiguously derive the four-point electromagnetic and gravitational Compton amplitudes for $s \leq 3/2$ and $s \leq 5/2$, which are uniquely determined by the on-shell recursion relation and are free from unphysical spurious poles. In addition, we explore amplitudes of spin-$3/2$ particles with non-minimal three-point interactions with photon, as well as $s > 3/2$ particles, and comment on their notable features. Our work furthers the understanding of on-shell methods for massive amplitudes, with hopes to shed light on physical observables in particle physics and higher-spin amplitudes relevant for Kerr black-hole scattering.

Speaker: Ishmam Mahbub (University of Minnesota Twin Cities)

AM Parallel: Top Physics 1

15 ATLAS results on top quark properties

The exceptionally large dataset collected by the ATLAS detector at the highest proton-proton collision energies provided by the LHC enables precision testing of theoretical predictions using an extensive sample of top quark events. New results on top-quark properties are shown. This includes the first observation of quantum entanglement in top-quark pair events and tests of lepton-flavour universality.

Speakers: ATLAS Speaker, Evelin Meoni (Universita della Calabria e INFN (IT))

16 Measurements of the top quark properties and its production at its kinematic threshold

Measurements of the top quark properties and its production at its kinematic threshold

Speaker: Niki Saoulidou (National and Kapodistrian University of Athens (GR))

17 ATLAS results on ttbar+heavy flavour measurements

The top-quark pair production in association with heavy-flavour jets (b/c) is a difficult process to calculate and model and is one of the leading sources of background to ttH and 4tops in 1l/2LOS channel. To improve our understanding of this process, new measurements of this process have been performed.

Speakers: ATLAS Speaker, Evelin Meoni (Universita della Calabria e INFN (IT))

18 Top quark production at the ttbar threshold

Near the threshold of top quark pair production, non-relativistic QCD predicts an enhancement of ttbar production in pseudoscalar states. Color-singlet contributions are expected to produce a distinct resonance just below the tt threshold, offering a unique testable signature at the LHC. In this talk, we present the first observation of such a contribution in the dileptonic final state. In addition, we will discuss first results in the lepton+jets channel, providing further evidence. These findings mark the beginning of a new chapter in top quark physics and open up a novel avenue for studying bound-state effects involving top quarks.

Speaker: Niki Saoulidou (National and Kapodistrian University of Athens (GR))

19 Toponium at the LHC

We study the signature of toponium at the LHC.

Speaker: Ya-Juan Zheng

Special Events: Lunch

AM Parallel: Accelerator Technologies 2

20 The US Magnet Development Program (MDP) Roadmap for future particle physics colliders.

The Particle Physics Project Prioritization Panel (P5), a decadal strategic planning exercise of the Particle Physics Community, has released their final report. The report is based on input from “Snowmass,” a scientific study to define the most important questions for the field of particle physics and identify promising opportunities to address them. Taking input from Snowmass, P5 lays out a strategic plan and sets priorities for the field. A broad range of proposals for future facilities were put forward, with a few targeting 10 TeV pCM energy. All of these require beyond state-of-the-art superconducting materials and magnets and the US Magnet Development Program has created an updated R&D Roadmap to align with the P5 priorities. Enabling such facilities will involve tackling a variety of challenges that will be described in this talk.

Speaker: Stephen Gourlay

21 800 MHz SRF R&D for FCC

800 MHz bulk niobium superconducting RF cavities are a fundamental, and sizeable, component of the FCC machine at all operating points. In the Booster, for Z, W, and H operating points, there are 112 cavities in 28 cryomodules. For TTbar operation, there will be a total of 448 cavities in the booster in 112 cryomodules, The FCC cavity performance specifications currently sit at the upper limit of what present-day techniques can achieve, and still incur a high RF power budget, in addition to generating substantial static and dynamic heat loads per cavity, driving up cryogenic costs. In order to deliver the most cost-effective and feasible version of the FCC, R&D efforts on 800 MHz SRF cavities and cryomodules have begun, focusing on advanced surface treatments for bulk niobium on 5-cell and single-cell 800 MHz prototypes. We report the first cold test results of these prototypes, and propose a course for future development. In addition, FNAL is collaborating with CERN on the mechanical design of the 6-cell 800 MHz cavities and cryomodules, based on experience with PIP-II designs and production. We thus also present updates and future plans for 800 MHz SRF CM R&D for FCC.

Speaker: Kellen McGee (Fermi National Accelerator Laboratory)

22 Rapidly Pulsed Schrotron Acceleration Chain for a Fermilab Sited Muon Collider

We present a preliminary lattice based on a bottom up design for a rapidly cycling synchrotron (RCS) accelerator chain for a multi-TeV muon collider based at Fermilab. The RCS rings range in circumference from 6.28 km (that of the Tevatron) to 15.5 km (the current estimate for the maximum that can be accommodated at the Fermilab site). Each ring is either a conventional RCS (consisting of iron dominated, ramped field magnets) or a hybrid RCS (consisting of interleaved ramped field and superconducting, coil dominated, fixed field magnets, which enable such rings to achieve higher average fields while retaining rapid ramping capabilities over their energy range). An injection energy of 63 GeV is used for the first ring (RCS 1). The tradeoff between the ultimate energy and the survival rate of the muons for different variants of the synchrotron chain is examined.

Speaker: Kyle Capobianco-Hogan

23 Modification of Generating Functions For Dynamic Aperture Enlargement

Particle accelerators are typically constrained in intensity of a beam due to a phenomenon known as the dynamic aperture (DA).  This DA is typically determined by the elemental components of the lattice under consideration and is often constricted by the presence of nonlinear elements, such as sextupole magnets.  However, the lattice may often be represented by an order $n$ Taylor map, which in turn may be used to find a corresponding generating function.  We examine the possibility of modifying the generating function that describes the map for a given lattice in such a way as to adjust only the nonlinear contributions to the map, while keeping the linear structure of the lattice the same, thereby increase the possible DA of the lattice.

Speaker: Mr Kevin Hamilton (Northern Illinois University)

AM Parallel: Charged Lepton Flavor Violation 2

AM Parallel: Dark Sectors (Direct/Indirect)

AM Parallel: Hadron Physics 1

AM Parallel: Heavy BSM Searches at Colliders 2

AM Parallel: Neutrino Physics 2

AM Parallel: Top Physics 2

15:30 Afternoon Break

PM Plenary: Monday Afternoon Plenary

Poster Session: Reception

Tuesday 26 August

AM Plenary: Tuesday

10:30 Morning Break

AM Parallel: Charged Lepton Flavor Violation 2

24 Latest results of $\mu \to e \gamma$ search with the MEG II experiment

The MEG II experiment searches for the lepton-flavor-violating muon decay, $\mu^+ \to e^+ \gamma$, utilizing the most intense continuous muon beam at Paul Scherrer Institut and innovative high-resolution detectors, with a target sensitivity of $6 \times 10^{-14}$. The experiment started collecting physics data in 2021 and has been accumulating statistics. The latest result, based on the data collected in 2021 and 2022, has achieved the most sensitive search to date. No signal excess was found, and the most stringent upper limit on the branching ratio was set to $1.5 \times 10^{-13}$ at the 90% confidence level. We will reach the sensitivity goal with further data acquisition anticipated by 2026 and analysis improvements. This presentation will provide the latest results and the prospects of the $\mu^+ \to e^+\gamma$ search with the MEG II experiment.

Speaker: Kensuke Yamamoto (The University of Tokyo)

25 The COMET Experiment for the Search of Muon-to-Electron Conversion

The COMET experiment aims to search for the process of muon-to-electron conversion in a muonic atom, with a ultimate goal of achieving a sensitivity on the order of 10$^{-17}$. This process violates the charged lepton flavor conservation and is forbidden in the Standard Model of the particle physics. Therefore, its discovery would be a clear evidence of the new physics. After the first engineering run for beam commissioning in 2023, the construction of the experimental facility and the detectors is now underway toward the physics run of the COMET Phase-I, which aims for a sensitivity of 3$\times$10$^{-15}$. The pion capture solenoid magnet, the largest experimental equipment, has already been installed, and delivery of the remaining detector solenoid is scheduled for this year. Following the magnets, the installation of the detector system will be carried out. This talk will provide an update on the current status of the COMET experiment construction.

Speaker: Yoshinori Fukao (High Energy Accelerator Research Organization)

26 Long-lived Axion-Like Particles from Tau Decays

Axion-like particles (ALPs) are well-motivated examples of light, weakly coupled particles in theories beyond the Standard Model. We study constraints on long-lived ALPs with mass between the electron and the tau mass, coupled exclusively to leptons. For anarchic flavor structure the leptophilic ALP production in tau decays or from ALP-tau bremsstrahlung is enhanced thanks to derivative couplings of the ALP and can surpass production from electron and muon channels, especially for ALPs heavier than the muon. Using past data from high-energy fixed-target experiments such as CHARM and BEBC we place new constraints on the ALP decay constant , reaching scales as high as $\mathcal{O}(10^8)$ GeV in lepton-flavor-violating channels and $f_a \sim \mathcal{O}(10^2)$ GeV in lepton-flavor-conserving ones. We also study projections for the event-rate sensitivity of current and future detectors to ALPs produced at the Fermilab Main Injector, the CERN SPS, and in the forward direction of the LHC. SHiP will be sensitive to $f_a$ values that are over an order of magnitude above the existing constraints.

Speaker: Patrick Fox

27 Direct Detection of Ultralight Dark Matter via Charged Lepton Flavor Violation

I will discuss a proposed dark matter direct-detection strategy using charged particle decays at accelerator-based experiments. If ultralight $(m_\phi \ll \text{eV})$ dark matter has a misalignment abundance, its local field oscillates in time at a frequency set by its mass. If it also couples to flavor-changing neutral currents, rare exotic decays such as $\mu \to e \phi'$ and $\tau\to e(\mu)\phi'$ inherit this modulation. Focusing on such charged lepton flavor-violating decays, we show that sufficient event samples can enable detection of ultralight dark matter candidates at Mu3e, Belle-II, and FCC-ee.

Speaker: Dr Innes Bigaran (Fermilab and Northwestern University)

28 Heavy and light new physics in rare muon decays

I will discuss signatures of muon-to-electron conversion arising from both heavy and light new physics at high-intensity rare muon decay experiments. For heavy new physics, I will outline a hierarchy of effective field theories for computing the rate of $\mu \to e$ conversion in the field of a nucleus, highlighting how different new physics scenarios imprint on nuclear responses relevant for experiments such as Mu2e and COMET. For light new physics, I will focus on the discovery potential and experimental reach of the $\mu \to 5e$ channel at Mu3e.

Speaker: Tony Menzo

AM Parallel: Future Colliders 1

29 A Linear Collider Vision for the Future of Particle Physics

We review linear e+e− colliders with a special focus on high centre-of-mass energies and beam polarisation, take a fresh look at the various accelerator technologies available or under development and, for the first time, discuss how a facility first equipped with a technology mature today could be upgraded with technologies of tomorrow to reach much higher energies and/or luminosities. In addition, we will discuss alternative collider modes, as well as opportunities for beyond-collider experiments and R&D facilities as part of a linear collider facility (LCF). The material of this presentation will support all plans for e+e− linear colliders and additional opportunities they offer, independently of technology choice or proposed site, as well as R&D for advanced accelerator technologies. This joint perspective on the physics goals, early technologies and upgrade strategies has been developed by the LCVision team. It heavily builds on decades of achievements of the global linear collider community, in particular in the context of ILC, CLIC and C3, and recent highlights of the projects will also be presented.

Speaker: Ivanka Bozovic-Jelisavcic (University of Belgrade (RS))

30 Progress of the Super Tau Charm Facility in China

The Super Tau Charm Facility (STCF), a planned symmetric electron-positron collider in China, aims to facilitate $e^+e^−$ collisions across a center-of-mass energy range of 2 to 7 GeV, targeting a peak luminosity of $0.5×10^{35}\mathrm{cm}^{−2}\mathrm{s}^{−1}$. With an anticipated annual integrated luminosity exceeding $1~ab^{−1}$, the STCF is poised to generate vast datasets. These will enable precision measurements of XYZ particles' properties, exploration of new CP violation sources within strange-hyperon and tau-lepton sectors, and accurate Cabibbo angle ($\theta_c$) measurements to test the unitarity of the CKM matrix; search for anomalous decays with sensitivities extending down to the level of SM-model expectations, among other objectives. This talk will cover the STCF's physics goals and outline the latest advancements in the project’s R&D.

Speaker: Qipeng Hu (University of Science and Technology of China (CN))

31 Gaseous detector R&D for FCC-ee

Gaseous detectors play a critical role in the design of the inner tracker and muon detector systems for the Future Circular Collider electron-positron (FCC-ee) experiment. When combined with a high-resolution pixel detector and a silicon strip wrapper, a gaseous detector enables exceptional tracking performance, achieving a transverse momentum resolution of 0.1–0.2% at 45 GeV. This represents a 5- to 10-fold improvement over the current capabilities of the ATLAS and CMS detectors at the same energy scale. Furthermore, the system resolves track angles with O(1 mrad) precision and provides O(100) hits along the track path, ensuring robust reconstruction of particle trajectories. In addition, the gaseous detector offers excellent particle identification capabilities by measuring energy deposition or the number of primary ionization clusters produced. This allows for excellent separation of charged pions and kaons across a broad momentum range from O(100 MeV) to O(40 GeV).

The muon detector is essential for muon identification and triggering. Precise measurements of charged particle segment directions and arrival times enable searches for exotic phenomena, such as long-lived particles and charged massive stable particles. To meet these demands, a design incorporating drift tubes and scintillator strips has been proposed, offering high spatial and temporal resolution, cost efficiency, and reliable performance.

This presentation will discuss the development of a straw tracker for the inner tracking system and a muon detector combining drift tubes and scintillator strips. Results from detailed simulations will be presented. In addition, experimental data from prototype detectors will be discussed, providing insights into their practical implementation and validating the simulation predictions. These advancements underscore the potential of gaseous detectors to significantly enhance the physics reach of the FCC-ee.

Speaker: Junjie Zhu (University of Michigan (US))

32 R&D Studies on the ALLEGRO Noble Liquid Calorimeter for FCC-ee

The Future Circular Collider in its first stage, an electron-positron collider (FCC-ee), presents a broad physics program with multiple challenges for detector design. It aims to enable precision measurements of the electroweak sector at an unprecedented level and facilitate searches for new particles weakly coupled to the Standard Model. ALLEGRO is one of the proposed detector concepts suitable for FCC-ee.

The electromagnetic calorimeter (ECAL) in ALLEGRO will utilize noble liquid technology, developed as a part of the Detector R&D Collaboration for Calorimeters (DRD6). The ECAL design has been optimized for FCC-ee, featuring a multilayer structure with straight readout electrodes that enable fine segmentation. This high granularity is crucial for advanced reconstruction techniques, including machine learning algorithms and particle flow methods. The performance of the readout electrodes will be discussed based on experimental measurements and compared with simulation results.

Additionally, intensive R&D efforts on the mechanical structure of the calorimeter (including absorber plates, support structures, and spacers) will be presented, along with progress toward a beam test prototype. The integration of the ALLEGRO detector geometry and reconstruction algorithms within the key4hep software framework will also be covered, highlighting expected performance.

Speaker: Jana Faltova (Charles University (CZ))

33 A Straw Tracker for FCC-ee Experiments

We propose to build a straw tracker as an inner tracking system for FCC-ee experiments. The straw tracker offers the advantage of a low material, a crucial factor in minimizing overall inner detector material budget. With the capability to achieve a single-hit resolution of approximately 100 microns per layer, and the potential for up to 100 layers, the straw tracker will play a pivotal role in pattern recognition and particle identification. Each individual straw serves as a standalone unit, facilitating easy removal of a channel in case of a broken sense wire. The electric field is radial symmetric and the hit position resolution is thus independent of the particle's incident angle. We will present performance studies based on GEANT simulations and cosmic ray data, along with preliminary results on particle identification using the primary cluster counting method (dN/dX).

Speaker: Jessaly Zhu

AM Parallel: Parallel 12

AM Parallel: Theory 2

34 BSM theory review

In this talk, I am going to review recent development of BSM theories.

Speaker: Peisi Huang

35 Bubble wall velocity calculation and implications for baryogenesis and gravitational waves

A precise determination of the bubble wall velocity $v_w$ is crucial for making accurate predictions of the baryon asymmetry and gravitational wave (GW) signals in models of electroweak baryogenesis (EWBG).
Working in the local thermal equilibrium approximation, we exploit entropy conservation to present efficient algorithms for computing $v_w$, significantly streamlining the calculation.
We then explore the parameter dependencies of $v_w$, focusing on two sample models capable of enabling a strong first-order electroweak phase transition: a $\mathbb{Z}_2$-symmetric singlet extension of the SM, and a model for baryogenesis with CP violation in the dark sector.
We study correlations among $v_w$ and the two common measures of phase transition strength, $\alpha_n$ and $v_n/T_n$.
Interestingly, we find a relatively model-insensitive relationship between $v_n/T_n$ and $\alpha_n$.
We also observe an upper bound on $\alpha_n$ for the deflagration/hybrid wall profiles naturally compatible with EWBG, the exact value for which varies between models, significantly impacting the strength of the GW signals.
In summary, our work provides a framework for exploring the feasibility of EWBG models in light of future GW signals.

Speakers: Isaac Wang, Isaac Wang

36 On-shell Recursion in Massive QED and Electroweak Theories

We study the All-Line Transverse (ALT) shift which we developed for on-shell recursion of amplitudes for particles of any mass. We apply the shift to unambiguously derive massive QED and electroweak theory amplitudes using on-shell methods. We discuss the validity of the shift for general theories of spin $\leq$ 1, and illustrate the connection between Ward identity and constructibility for massive spin-1 amplitude under the ALT shift. We show explicitly that the four-point gauge boson contact terms in massive electroweak theory automatically arise after recursive construction, independent of UV completion, and they automatically cancel the terms growing as (energy)$^4$ at high energy. We explore UV completion of the electroweak theory that cancels the remaining (energy)$^2$ terms and impose unitarity requirements to constrain additional couplings. The ALT shift framework allows consistent treatment in dealing with contact term ambiguities for renormalizable massive and massless theories, which we show can be useful in studying real-world amplitudes with massive spinors.

Speaker: Ishmam Mahbub (University of Minnesota Twin Cities)

37 Cheshire θ terms, Aharonov-Bohm effects, and axions

We discuss unusual θ terms that can appear in field theories that allow global vortices. These "Cheshire θ terms" induce Aharonov-Bohm effects for some particles that move around vortices. For example, a Cheshire θ term can appear in QCD coupled to an axion and induces Aharonov-Bohm effects for baryons and leptons moving around axion strings. We point out a potential experimental signature left on the spectrum of gravitational waves from axion cosmic string network by the Cheshire θ term.

Speaker: Gongjun Choi

Special Events: Lunch

AM Parallel: Parallel 13

AM Parallel: Parallel 14

AM Parallel: Parallel 15

AM Parallel: Parallel 16

15:30 Afternoon Break

PM Plenary: Tuesday

Poster Session: Judging

Wednesday 27 August

AM Plenary: Wednesday

10:30 Morning Break

AM Parallel: Future Colliders 2

38 The IDEA detector concept for FCC-ee

The electron-positron stage of the Future Circular Collider (FCC-ee) provides exciting opportunities that are enabled by next generation particle physics detectors. We present IDEA, a detector concept optimized for FCC-ee and composed of a vertex detector based on DMAPS, a very light drift chamber, a silicon wrapper, a high resolution dual-readout crystal electromagnetic calorimeter, an HTS based superconducting solenoid, a dual-readout fiber calorimeter, and three layers of muon chambers embedded in the magnet flux return yoke. In particular, we discuss the physics requirements and the technical solutions chosen to address them. We describe the detector R&D currently in progress, test-beam results, and show the expected performance on a selection of key physics benchmarks.

Speaker: Wonyong Chung (Princeton University (US))

39 MUSIC: a detector concept for 10 TeV $\mu^+\mu^-$ collisions

The full exploitation of the physics potential of a multi-TeV muon collider will ultimately lie in the detector's ability to cope with unprecedented levels of machine-induced backgrounds. This contribution introduces the MUSIC (MUon System for Interesting Collisions) detector concept and presents its performance in the context of $\sqrt{s}$ = 10 TeV muon-antimuon collisions. The MUSIC detector is designed to mitigate machine-induced background effects while maintaining high efficiency and accuracy in the reconstruction of physics events, in particular in the Higgs boson sector and in the search for new physics. It features an advanced all-silicon tracking system, a semi-homogeneous lead-fluorite crystal electromagnetic calorimeter, a iron-scintillator sampling hadronic calorimeter, and a superconducting magnet providing a 5 T magnetic field.
The contribution presents the results of detailed detector simulations including the dominant machine-induced backgrounds. The results demonstrate promising tracking efficiency, photon, electron and jet reconstruction capabilities, and jet flavor identification performance, highlighting the strong potential of the detector for high-energy muon collider experiments.

Speakers: Alessio Gianelle (Universita e INFN, Padova (IT)), Davide Zuliani (Universita e INFN, Padova (IT)), Donatella Lucchesi (Universita e INFN, Padova (IT)), Leonardo Palombini (INFN-Padova, Italy), Lorenzo Sestini (Universita e INFN, Firenze (IT)), Massimo Casarsa (INFN, Trieste (IT)), Paolo Andreetto (Universita e INFN, Padova (IT))

40 CyberPFA: Particle Flow Algorithm for Crystal Bar ECAL

Precision measurements of Higgs, W, and Z bosons at future lepton colliders demand jet energy reconstruction with unprecedented accuracy. The particle flow (PFA) approach has proven to be highly effective in achieving the required jet energy resolution. CyberPFA is a novel particle flow algorithm specifically designed for the crystal bar electromagnetic
calorimeter (ECAL) in the CEPC reference detector. This innovative calorimeter design combines superior intrinsic energy resolution with cost efficiency but introduces two critical reconstruction challenges: (1). Severe shower overlaps due to the material's large Molière radius ($R_M$) and large ratio of radiation length (X0) to nuclear interaction length ($\lambda_I$). (2) Ambbiguity problem caused by the perpendicular arrangement of crystal bars.

To overcome these challenges, CyberPFA introduces a breakthrough energy-core-based pattern recognition method, followed by an energy-splitting process to resolve overlapping showers. Additionally, multiple optimized pattern recognition techniques are implemented to address the ambiguity problem. Integrated with full detector simulation, CyberPFA achieves a 3.8% boson mass resolution for hadronic decays, surpassing the critical 4% threshold required for $W/Z$ separation.

These results demonstrate that: The long crystal bar ECAL is a viable and high-performance option for future colliders. CyberPFA’s energy-core-based reconstruction paradigm provides a novel and effective solution to imaging calorimeter reconstruction, specifically overcoming the critical challenges of shower overlaps in high-density environments. The algorithm’s innovative shower recognition approach is not only optimized for the current design but also adaptable to other imaging calorimeters, potentially enhancing their performance.

Speaker: Yang Zhang (Institute of High Energy Physics, Chinese Academy of Science)

41 Smart Pixels at a Muon Collider

A muon collider offers a means for reaching higher energies by combining the advantages of electron-positron and proton-proton colliders. Beam induced background (BIB), which results from muon decays in the beam, poses a significant challenge for detector design and readout. The pixel detector sits at the heart of the detector and is subjected to the largest rate of BIB. The bandwidth required to send all of the resulting signals off-detector is prohibitive. To overcome this challenge, we propose to develop “smart” pixels with a neural network implemented in front-end electronics to differentiate between clusters of hits produced by BIB and collision particles. We investigate properties of pixel clusters in simulation, and present a neural network that can selectively read out clusters of interest.

Speaker: Eliza Claire Howard (University of Chicago (US))

42 Light Axion-Like Particles at Future Lepton Colliders

Axion-like particles (ALPs) are well-motivated extensions of the Standard Model (SM) that appear in many new physics scenarios, with masses spanning a broad range. In this work, we systematically study the production and detection prospects of light ALPs at future lepton colliders, including electron-positron and multi-TeV muon colliders. At lepton colliders, light ALPs can be produced in association with a photon or a Z boson. For very light ALPs (ma < 1 MeV), the ALPs are typically long-lived and escape detection, leading to a mono-V (V = γ, Z) signature. In the long-lived limit, we find that the mono-photon channel at the Tera-Z stage of future electron-positron colliders provides the strongest constraints on ALP couplings to SM gauge bosons, gaVV, thanks to the high luminosity, low background, and resonant enhancement from on-shell Z bosons. At higher energies, the mono-photon cross section becomes nearly energy-independent, and the sensitivity is governed by luminosity and background. At multi-TeV muon colliders, the mono-Z channel can yield complementary constraints. For heavier ALPs (ma > 100 MeV) that decay promptly, mono-V signatures are no longer valid. In this case, ALPs can be probed via non-resonant vector boson scattering (VBS) processes, where the ALP is exchanged off-shell, leading to kinematic deviations from SM expectations. We analyze constraints from both light-by-light scattering and electroweak VBS, the latter only accessible at TeV-scale colliders. While generally weaker, these constraints are robust and model-independent. Our combined analysis shows that mono-V and non-resonant VBS channels provide powerful and complementary probes of ALP-gauge
boson interactions.

Speaker: Keping Xie (Michigan State University)

AM Parallel: Parallel 17

AM Parallel: Parallel 19

AM Parallel: Triggers AI/ML

43 Online track reconstruction with graph neural networks on FPGAs for the ATLAS experiment

The High-Luminosity Large Hadron Collider (HL-LHC) at CERN marks a
new era for high-energy particle physics, demanding significant
upgrades to the ATLAS Trigger and Data Acquisition (TDAQ) system.
Central to these upgrades is the enhancement of online software
tracking capabilities to meet the unprecedented data rates and
complexity of HL-LHC operations. This study investigates the
deployment of Graph Neural Networks (GNNs) on Field-Programmable
Gate Arrays (FPGAs) within the Event Filter system of the ATLAS
experiment. Focusing on the reconstruction of tracks in the new
all-silicon ATLAS Inner Tracker, we detail a GNN-based tracking
pipeline comprising graph construction, edge classification via
interaction networks, and segmentation into track candidates. Key
optimizations, including model hyperparameter tuning, pruning,
quantization-aware training, and sequential processing of detector
regions, are explored to reduce FPGA resource utilization and
maximize throughput. Our results demonstrate the potential of this
approach to achieve high tracking efficiency and low fake rates,
aligning with the stringent requirements of the ATLAS Event Filter
system for HL-LHC operations.

Speaker: ATLAS Speaker

44 Run 3 CMS Trigger Developments for New Physics Exploration

Run 3 CMS Trigger Developments for New Physics Exploration

Speaker: Niki Saoulidou (National and Kapodistrian University of Athens (GR))

45 Strategies and Performances of the CMS Trigger in Run 3

Strategies and Performances of the CMS Trigger in Run 3

Speaker: Niki Saoulidou (National and Kapodistrian University of Athens (GR))

46 GELATO: A Generic Event-Level Anomalous Trigger Option for ATLAS in LHC Run 3

Search for physics beyond the Standard Model has been a long-standing subject at the LHC. The absence of such signatures indicates that new physics may elude standard triggers; conventional triggers at the ATLAS experiment are constructed by setting thresholds on variables such as the particle momentum, targeting event topologies exclusive to specific models. Anomaly detection, a form of unsupervised machine learning, enables searches for signatures which deviate from the Standard Model without relying on particular model assumptions. We present the first anomaly detection trigger at ATLAS, newly developed and integrated for data-taking in LHC Run 3. In addition to its design and expected performance, we discuss its commissioning, validation, and operational robustness, along with some look in the newly collected data. The first anomaly detection trigger in ATLAS marks a milestone for machine learning-based, next-generation triggers and model-agnostic searches for new physics.

Speaker: ATLAS Speaker

47 CICADA: Real-Time Anomaly Detection with Calorimeter Images at the CMS Level-1 Trigger

CICADA: Real-Time Anomaly Detection with Calorimeter Images at the CMS Level-1 Trigger

Speaker: Niki Saoulidou (National and Kapodistrian University of Athens (GR))

Special Events: Lunch

AM Parallel: Parallel 21

AM Parallel: Parallel 22

AM Parallel: Parallel 23

AM Parallel: Parallel 24

15:30 Afternoon Break

PM Plenary: Wednesday

Community Events: Explore Downtown Madison!

19:00 Banquet

Thursday 28 August

AM Plenary: Thursday

10:30 Morning Break

AM Parallel: Future Colliders 3

48 Overview of the FCC Program

The Future Circular Collider (FCC) is a visionary international endeavor aimed at pushing the frontiers of particle physics beyond the capabilities of the LHC. This talk provides an overview of the FCC program, including its scientific goals, technological challenges, and implementation strategy. From precision studies of the Higgs boson to the exploration of new physics at unprecedented energies, the FCC represents a long-term roadmap for the next generation of high-energy colliders.

Speaker: Markus Klute (Karlsruhe Inst. of Technology (GER))

49 BSM physics opportunities at the FCC-ee

The electron-positron stage of the Future Circular Collider (FCC-ee) is a precision frontier factory for Higgs, electroweak, flavour, top quark, and QCD physics. It is designed to operate in a 91-km circular tunnel built at CERN, and will serve as the first step towards O(100 TeV) proton-proton collisions. In addition to an essential Higgs program, the FCC-ee offers unique and powerful opportunities to answer fundamental open questions and explore unknown physics beyond the Standard Model. Direct searches for long-lived particles, and indirect probes of new physics sensitive to several tens of TeV scale, will be particularly fertile in the high-luminosity Z run, where $8×10^{12}$ Z bosons are expected. The large data samples of Higgs bosons, W bosons, and top quarks in very clean experimental conditions will offer additional opportunities for discoveries at other collision energies. Three concrete physics cases with promising signatures at FCC-ee will be discussed: heavy neutral leptons (HNLs), axion-like particles (ALPs), and exotic decays of the Higgs boson. These three well-motivated cases motivate out-of-the-box optimization of experimental conditions and analysis techniques that could lead to improvements in other searches for new physics.

Speaker: Markus Klute (Karlsruhe Inst. of Technology (GER))

50 Detector Challenges at a Muon Collider

Detector Challenges at a Muon Collider

Speaker: Karri Folan Di Petrillo (University of Chicago)

51 Pixel-based BIB suppression and DAQ impact at a multi-TeV Muon Collider

The muon collider stands out as a compelling option for future high-energy physics experiments, combining unique physics potential with significant technical challenges. One of the most critical issues is the intense beam-induced background (BIB) from muon decays, which produces low-momentum particles that lead to high detector occupancies, complicating vertexing, tracking, and overwhelming simulation resources and readout systems. This talk presents recent advances in BIB mitigation through a detailed pixel-level analysis within the official Muon Collider software framework. A central strategy is the development of a novel cluster shape analysis, leveraging correlations among pixel cluster size, charge, incidence angle, and timing to distinguish signal from background. In parallel, we investigate the impact of increased active sensor thickness - trading some precise timing resolution for improved charge deposition from minimum-ionizing muons, which enhances separation between signal and soft BIB secondaries. This enables more effective rejection of background hits through optimized thresholds and refined shape-based filtering. We demonstrate the combined impact of these techniques in reducing BIB hit rates and data bandwidth, while preserving high signal efficiency in track reconstruction. Preliminary results from high-statistics simulation will be presented, along with insights into expected readout rates, dead time, power budgets, and the potential for a simplified trigger scheme.

Speaker: Angira Rastogi (Lawrence Berkeley National Lab. (US))

AM Parallel: Parallel 25

AM Parallel: Parallel 27

AM Parallel: Parallel 28

Special Events: Lunch

AM Parallel: Parallel 30

AM Parallel: Parallel 31

AM Parallel: Parallel 32

AM Parallel: Top Physics 3

15:30 Afternoon Break

PM Plenary: Thursday

17:30 Walk to UW Campus

Community Events: Public Lecture on UW Campus

Friday 29 August

AM Plenary: Friday 1

10:30 Morning Break

AM Plenary: Friday 2

Special Events: Lunch

PM Plenary: Friday 3

15:00 Afternoon Break

PM Plenary: Closing

17:30 Free time

Community Events: Dane Dances - Rooftop Dance Party