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    LLP2026: 16th workshop of the Long-Lived Particle Community

    → Europe/London
    Ray Dolby Centre

    Ray Dolby Centre

    J J Thomson Avenue, Cambridge, CB3 0US, UK
    Description

    The sixteenth workshop of the Long-Lived Particle Community will run from 29 June to 3 July, 2026 at the Cavendish Laboratory, University of Cambridge, GB (map).

    Short URL: https://indico.cern.ch/e/LLP_2026

    We have a Mattermost channel for discussions during the workshop.

    A reminder of the CERN code of conduct.

    Highlights

    • Workshop atmosphere!
    • Two Hackathlon-style hands-on sessions focused on reinterpretation of LLP searches
    • Abstract submission opens on 9 March
    • Drinks reception with poster session on Monday
    • Social programme:
      • Guided tour through historic colleges of the fourth-oldest University in the world (est. 1209)
      • Dinner in a historic College (Sidney Sussex College)
    • Arrival by Monday lunchtime, departure Friday lunchtime

     

    For accommodation, we recommend booking on your own, using standard providers like e.g., booking.com.
    There are several close options (Hyatt Centric Cambridge, Premier Inn Cambridge North, Turing Locke) and other options a little bit further away but still within walking distance (<30 min) in the city centre (Premier Inn Corn Exchange, Hilton Cambridge City Centre).

    Scientific committee (llp2026-oc@cern.ch):

    Sagar Addepalli
    Juliette Alimena
    James Beacham
    Lisa Benato
    Matthew Citron
    Albert de Roeck
    Jan Hajer
    Audrey Kvam
    Federico Leo Redi
    Arantza Oyanguren Campos
    Elena Pompa Pacchi
    Mason Proffitt
    Neha Santpur
    Emma Torró
    Andrii Usachov
    Carlos Vázquez Sierra
    José Zurita

    Local organizing committee (llp2026-loc@cern.ch):

    Oleg Brandt
    Cayetano Fernandez-Ruiz
    Nikolai Fomin
    Jack Gargan
    Tina Potter
    Michael Revering
    Aashaq Shah
    Paul Swallow
    Julian Wack

    LLP 2026 poster
    Local Organisers
    Participants
    74 View full list
    • Monday 29 June
      • Arrival and registration
      • 1
        Welcome to Cambridge
        Speaker: Oleg Brandt (University of Cambridge (GB))
        2026_06_29_LLPWS2026_welcome.pdf
      • 2
        Latest searches for LLPs at LHCb

        The exploration of long-lived particles (LLPs) provides a powerful avenue to probe physics beyond the Standard Model, with particular sensitivity to feebly interacting states that escape conventional prompt searches. The LHCb experiment, with its forward acceptance, excellent vertexing and mass resolution, and flexible trigger strategy, is uniquely positioned to study displaced decays over a broad kinematic range.

        In this contribution, the latest LHCb results on searches for LLPs are presented, setting the focus on heavy neutral leptons (HNLs) and axion-like particles (ALPs). The HNL search targets particles produced in heavy-flavour decays and decaying at macroscopic distances from the primary vertex, while the ALP search probes rare B-meson decays into multimuon final states, exploiting LHCb’s excellent mass resolution to identify narrow resonances.

        Finally, prospects for future analyses are discussed, including the impact of detector upgrades and novel trigger strategies that will further enhance sensitivity to long-lived signatures in Run 3 and beyond.

        Speaker: Felicia Volle (University of Birmingham (GB))
        LLPworkshop_Cambridge.pdf
      • Session 1: Poster Appetisers #1
        LLP2026_AppetizerTalks_Block1.pdf
        LLP2026_AppetizerTalks_Block2.pdf
        LLP2026_AppetizerTalks_Block3.pdf
      • 8
        CMS overview

        CMS summary overview talk.

        Speaker: Kai Hong Law (Imperial College (GB))
        LLP2026-CMS-overview_final.pdf
      • Session 1: Poster Appetisers #2
        LLP2026_AppetizerTalks_Block1.pdf
        LLP2026_AppetizerTalks_Block2.pdf
        LLP2026_AppetizerTalks_Block3.pdf
      • 14
        Recent Results of Long-Lived Particle Searches at ATLAS

        ATLAS summary overview talk.

        Speaker: Paul Nathaniel Swallow (University of Cambridge (GB))
        PSwallow_20260629_ATLASLLPOverview.pdf
      • Session 1: Poster Appetisers #3
        LLP2026_AppetizerTalks_Block1.pdf
        LLP2026_AppetizerTalks_Block2.pdf
        LLP2026_AppetizerTalks_Block3.pdf
      • 15:50
        Coffee/Tea Break
      • 21
        Updated Results from the milliQan Experiment

        We will give an update from the milliQan experiment at CERN. The milliQan "bar" detector was completed in 2023 and has been taking physics data since then. The milliQan "slab" detector was completed in 2024 and has been taking physics data since 2025. We will give an update on the readiness of the slab detector for physics data taking. We will present updated results on the search for millicharged particles in 13.6 TeV proton collision data recorded by both the bar and slab detectors during LHC Run 3.

        Speaker: Juan Salvador Tafoya Vargas (University of California Davis (US))
        LLP2026 Cambridge - MilliQan.pdf
      • 22
        Search for long-lived particles using displaced vertices of oppositely charged leptons in 140 fb^{-1} of pp collisions at \sqrt{s} = 13 TeV with the ATLAS detector

        A search is presented for long-lived particles decaying into an oppositely charged lepton pair, $\mu^{+}\mu^{-}$, $e^{+}e^{-}$, or $e^{\pm}\mu^{\mp}$, that form a vertex within the inner tracking system of the ATLAS detector at the Large Hadron Collider, displaced from the primary proton-proton interaction region. The analysis uses the $140 fb^{-1}$ of Run-2 data collected at $\sqrt{s}=13$ TeV by the ATLAS experiment in 2015-2018. The results of the analysis are interpreted in the context of three benchmark models covering masses from 0.1 to 2.2 TeV and a range of mean proper lifetimes times the speed of light from 1 to 10000 mm. The first model is a generic Z' boson pair-produced by a new heavy scalar, with the Z' decaying into lepton pairs. The remaining two models are R-parity violating supersymmetric models in which the lightest neutralino $\tilde{\chi}^{0}_{1}$ decays into $\ell^{+}\ell^{'-}\nu$ ($\ell, \ell^{'} = e, \mu$). The models differ by the mode of production of the $\tilde{\chi}^{0}_{1}$, which can be produced via the decay of pairs of gluinos or of pairs of charginos and neutralinos ($\tilde{\chi}_{1}^{\pm}\tilde{\chi}_{1}^{0}$, $\tilde{\chi}_{1}^{\pm}\tilde{\chi}_{2}^{0}$, or $\tilde{\chi}_{2}^{0}\tilde{\chi}_{1}^{0}$). Although each benchmark sample includes pair-produced LLPs, only a single vertex is required to be reconstructed. No dilepton displaced vertex candidate is observed, and the results are presented as upper limits on the production cross-sections. This analysis sets leading limits on the production cross-sections for multiple models, including parameter space that has never been directly probed.

        Speaker: Neil Andrew Pohl (Ohio State University (US))
        LLP_Talk_v5.pdf
      • 23
        Search for Axion-Like Particles in a Beam-Dump Experiment at KEK LINAC (EBES)

        Axion-like particles (ALPs) in the MeV–GeV range are well motivated by cosmology. They can arise as dark matter via thermal or non-thermal production, while inflationary dynamics shape their initial abundance. This parameter space satisfies cosmological constraints and remains accessible to accelerator experiments, enabling direct probes of early-Universe physics.
        EBES (Electron Beam-dump Experiment at KEK LINAC Switching Yard 3) is a beam-dump experiment designed to search for axion-like particles (ALPs) that couple to photons in the MeV–GeV mass range. The experiment uses a 4 GeV beam provided by the KEK LINAC, which is directed onto a tungsten fixed target. ALPs produced in the target are detected via their decay into two photons, measured with a calorimeter composed of lead-glass Cherenkov detectors.
        A pilot run conducted in December 2023 collected a dataset corresponding to $1.3 \times 10^{14}$ positrons on target. The pilot setup featured a decay volume of 28 cm, while the ALP decay length depends on the ALP mass, coupling, and boost; for example, assuming a momentum of 3.5 GeV, it is ~ 297 cm ($\tau_{a} \sim 2.35 \times 10^{-10}$ s) for $m_{a} = 85.1 \,\mathrm{MeV}$ and $g_{aγγ} = 3.02 × 10^{-8} \,\mathrm{MeV}^{-1}$. In October 2025, the first physics run with the Phase-1 setup was carried out. This configuration features a hollow, cone-shaped shield and an increased number of lead-glass Cherenkov detectors. The Phase-1 run collected a dataset of ~ $2.1 \times 10^{15}$ positrons on target.
        In this presentation, we will report the results of the pilot run analysis as well as the current status of the Phase-1 physics run analysis, and present the parameter space that can be probed by the EBES. We will also discuss future upgrade plans for EBES.

        Speaker: Fumihito IKEDA (School of Science, The University of Tokyo (Ootani-LAB))
        fikeda-20260629-llp.pdf
      • 24
        Strategy and performance of the CMS long-lived particle trigger program in Run 3

        In the physics program of the CMS experiment during the CERN LHC Run 3, which started in 2022, the long-lived particle triggers have been improved and extended to expand the scope of the corresponding searches. These dedicated triggers and their performance are described in this talk, using several theoretical benchmark models that extend the standard model of particle physics. The results are based on proton-proton collision data collected with the CMS detector during 2022--2024 at a center-of-mass energy of 13.6 TeV, corresponding to integrated luminosities of up to 123 fb-1.

        Speaker: Juliette Alimena (DESY)
        CMSLLPTriggers_LLPWorkshop_29June2026.pdf
      • 25
        Precision measurements and searches with metre-scale displaced vertices at LHCb

        The recent upgrade of the LHCb trigger and reconstruction system enables, for the first time, the efficient reconstruction of decay vertices using only tracks in the downstream tracking stations (T tracks), extending the fiducial decay volume up to about 8 m from the interaction point. This opens a unique window on the study of metre-scale displaced decays. The talk highlights how highly displaced vertex reconstruction at LHCb can be performed in real time and offline providing new opportunities for both precision measurements and searches for physics beyond the Standard Model. Currently, two physics programmes exploiting these capabilities are ongoing, namely searches for long-lived particles (LLPs) and measurements of the magnetic and electric dipole moments (MDM/EDM) of the Λ baryon and antibaryon through their spin precession in the LHCb magnetic field.

        Speaker: Izaac Sanderswood (Univ. of Valencia and CSIC (ES))
        sanderswood_llp2026_v2.pdf
      • Reception and Poster Session
    • Tuesday 30 June
      • Hands-on Session: Session 1
        Hackathon Materials
        • 26
          Session Intro
          Speaker: Dr José Francisco Zurita (IFIC, CSIC‐UV)
          Zurita_HACKATHON_intro.pdf
        • 27
          Hackathon Session
          Speakers: Federico Leo Redi (U. of Bergamo and INFN Milan (IT)), Jack Gargan (University of Cambridge (GB)), Tomasz Procter (Jagiellonian University (PL))
      • 10:40
        Coffee/Tea Break
      • Hands-on Session: Session 2
        Hackathon Materials
      • 12:30
        Lunch
      • 28
        The Forward Physics Facility

        The Forward Physics Facility (FPF) is a proposal developed to exploit the unique scientific potential made possible by the intense hadron beams produced in the far-forward direction at the high luminosity LHC (HL-LHC). The physics case for the FPF has continued to grow, and plans have matured on defining the facility and its experiments to realize this physics potential in a timely and cost-effective manner. This talk will summarize recent progress for the FPF as detailed in the recent letter of intent, https://arxiv.org/abs/2510.26260.

        Speaker: John Kenneth Anders (University of Liverpool (GB))
        LLP2026-FPF.pdf
      • 29
        Search for Soft Unclustered Energy Patterns containing muons in the final state in pp collisions at 13 TeV with the ATLAS detector

        Soft unclustered energy patterns (SUEPs) are characterized by high-multiplicity, isotropic distributions of low-momentum particles. The search for SUEPs containing muons in the final state is presented using 140 fb^−1 of proton–proton collision data collected by the ATLAS detector at the Large Hadron Collider during 2015–2018. The analysis targets SUEP signatures produced via gluon–gluon fusion of a scalar mediator in Hidden Valley scenarios. This is the first result in the ATLAS experiment.

        Speaker: Dr Ligang Xia (Nanjing University (CN))
        suep_search_ligang_LLP2026-v3p1.pdf
      • 30
        Long-lived particle searches at FASER and future machines

        In this work we study the prospect of detecting light scalars at the FASER, Mathusla codex-B etc. We develop the general formalism for the scalar production and decay from mesons with PP collision, given modified couplings of the scalars to the SM particles, as well as summarizing the relevant GeV-scale experiment constraints. We then analyze the reaches of light scalars in the large tan𝛽 region of the Type-I 2HDM, in which a light scalar with relatively long lifetime could be accommodated. We also have studies in the SUSY framework.

        Speaker: Wei Su (Sun Yat-sen University)
        LLP2026-WEISU.pdf
      • 31
        Ultra-displaced dimuon vertexing for long-lived particle signatures in ATLAS

        This talk presents a new secondary-vertexing technique based exclusively on StandAlone muon tracks reconstructed in the ATLAS Muon Spectrometer. These tracks, formed from Muon Spectrometer measurements without an associated Inner Detector track, naturally arise from highly displaced muon decays and are extremely rare for Standard Model processes. By exploiting the full detector-wide track extrapolation model and a dedicated Kalman-filter-based vertex fit, this method enables the reconstruction of dimuon vertices throughout the ATLAS detector volume, well beyond the reach of conventional Inner Detector–based approaches.

        The algorithm is demonstrated on benchmark LLP scenarios spanning a wide range of masses, boosts, and decay topologies, and is validated in Run~3 data using a novel tag-and-probe strategy based on $J/\psi \to \mu\mu$ decays reconstructed solely with Muon Spectrometer information. This approach opens access to a previously unexplored region of LLP phase space and provides a powerful new tool for the ATLAS long-lived particle search program.

        Speaker: Andrew Toler 🦝 (University of Massachusetts Amherst (US))
        Ultra-Displaced Dimuon Vertexing for Long-Lived Particle Signatures in ATLAS.pdf
      • 32
        Lepton Number Violation at Hadron Colliders

        Symmetry-protected low-scale type-I seesaw models can explain the observed pattern of neutrino masses while predicting collider-accessible heavy neutral leptons (HNLs) that appear as pseudo-Dirac pairs. In such scenarios, lepton-number (LN) violation is strongly suppressed at the amplitude level by the approximate LN-like symmetry. However, a realistic treatment of HNL production, propagation, and decay, including finite lifetimes, neutrino-antineutrino oscillations, and decoherence effects, can substantially modify this expectation. These effects govern the transition between LN-conserving and LN-violating signatures and introduce a critical mass-splitting scale above which decoherence enhances observable LN violation. While oscillation effects are especially relevant for long-lived HNLs, they also impact prompt collider searches. We compare the sensitivity of LN-violating and LN-blind search channels at hadron colliders, identify the parameter regions in which LN-violating searches remain competitive, and emphasize the need to reinterpret existing searches beyond the Dirac and Majorana limits.

        Speaker: Mr Bruno M. S. Oliveira (Centro de Física Teórica de Partículas (CFTP), Instituto Superior Técnico (IST), Universidade de Lisboa (UL))
        Bruno M. S. Oliveira - Lepton Number Violation at Hadron Colliders (LLP2026).pdf
      • 15:30
        Coffee/Tea Break
      • 33
        The BSM Physics Programme in ALICE: Probing Long-Lived Particles with the TPC

        In this talk, a hybrid detector strategy targeting Beyond the Standard Model (BSM) highly ionizing particles (HIPs) and long-lived particles (LLPs) within the ALICE experiment is presented. The approach combines an FPGA-based hardware trigger in the Time Projection Chamber (TPC) during online processing with an offline trigger based on the Inner Tracking System (ITS), together with dedicated reconstruction of the raw data.
        This strategy overcomes intrinsic limitations of standard readout and reconstruction algorithms optimized for Standard Model particles. Magnetic monopoles serve as a benchmark to demonstrate the concept and expected performance, while sensitivity extends to a broader class of highly ionizing LLP signatures. In addition, ALICE has recorded data at 2.4 TeV with a low-gain TPC configuration for HIP searches, for which dedicated reconstruction algorithms tailored to these unconventional signatures are employed.
        A similar concept is foreseen for ALICE 3, where the trigger would exploit the three innermost Inner Tracker (IT) layers inside the beam pipe together with the inner Time-of-Flight (TOF) detector at a radius of about 19 cm. This low-material configuration, combined with the closest TOF detector to the interaction point, provides a unique setup among LHC experiments for early identification of highly ionizing particles, enhancing sensitivity to rare exotic states.

        Speaker: Tuba Gundem (Goethe University Frankfurt (DE))
        LLP26_20260629_TubaGundem_final.pdf
      • 34
        Revising mass bounds for highly ionising particles after resummation

        Magnetic Monopoles (MM) and high-electric-charge objects (HECOs) are highly ionising particles actively searched for at the LHC. Unfortunately, due to their large couplings, tree-level cross sections, and the resulting mass limits, are in principle unreliable.
        We present analytical results from loop resummation techniques à la Dyson and Schwinger in strongly coupled gauge theories in the cases of (structureless) MMs and HECOs. The resummed effective theories are characterised by appropriate non-trivial ultraviolet (UV) fixed points, thus defining the theory to be used in experimental searches.
        For spin-1/2 monopoles, we employ a U(1)xU(1) effective field theory with a dual strongly-coupled dark photon. For spin-1/2 and spin-0 HECOs, we work within strongly coupled QED, where scalar HECOs require sufficiently strong self-interactions to stabilise the non-perturbative UV fixed point.
        This scheme provides theoretically reliable production cross sections, enabling robust mass bounds for MMs and significantly improved constraints for HECOs from ATLAS and MoEDAL searches compared to tree-level estimates. In the MM resummed case, we reproduce exactly the tree-level processes used in collider searches, therefore justifying the obtained mass bounds.

        1. J Alexandre, N E Mavromatos, V A Mitsou and E Musumeci, "Resummation schemes for High-Electric-Charge Objects leading to improved experimental mass limits,"
          PRD 109 (2024) 036026 [DOI: 10.1103/PhysRevD.109.036026]

        2. J Alexandre, N E Mavromatos, V A Mitsou and E Musumeci, "Impact of resummation on the production and experimental bounds of scalar high-electric-charge objects,"
          PRD 111 (2025) 076010 [DOI: 10.1103/PhysRevD.111.076010]

        3. J Alexandre, N E Mavromatos, V A Mitsou and E Musumeci, "Magnetic-monopole resummation justifies perturbatively calculated collider production cross sections," arXiv:2603.24200 [hep-ph]

        Speaker: Dr Vasiliki Mitsou (IFIC, CSIC-UV)
        Mitsou-resummation.pdf
      • 35
        The SHiP/NA67 experiment at the ECN3 high-intensity beam facility at the CERN SPS

        The SHiP/NA67 experiment is a general-purpose intensity-frontier experiment for the search for feebly interacting GeV-scale particles and to perform neutrino physics measurements at the HI-ECN3 (high-intensity) beam facility at the CERN SPS, operated in beam-dump mode, taking full advantage of the available $4\times 10^{19}$ protons per year at 400 GeV. The collaboration is currently optimising the experiment's initial configuration for the commissioning and first physics runs of 2032-2033.
        The setup consists of two complementary detector systems downstream of an active muon shield: the scattering and neutrino detector (SND), which includes a light dark matter (LDM) neutrino target with vertexing capability. and the hidden sector decay spectrometer (HSDS), consisting of a 50 m long decay volume followed by a spectrometer, timing detector, and a PID system. BDF/SHiP offers unprecedented sensitivity to the decay and scattering signatures of various new physics models and to tau neutrino physics.

        Speaker: Dr Anne-Marie Magnan (Imperial College (GB))
        SHiP_LLP2026.pdf
      • 36
        Proposing GRENDEL: a new dedicated LLP detector at the LHC

        We propose GRENDEL (GalleRy ExperimeNt for Decays of Exotic LLPs), a dedicated LLP detector to be installed in the existing PX56 drainage gallery at CMS Point 5. The gallery sits approximately 22 m above the CMS interaction point, with CMS detector material and 15--20 m of rock and concrete providing shielding from hadronic backgrounds and roughly 70 m of overburden suppressing the cosmic-ray muon flux. The existing tunnel geometry provides an air-filled decay volume of ~740m3 requiring no new civil engineering. We consider two potential technologies for tracking the decays of LLPs within the decay volume: extruded scintillator strips and scintillating fibres. We present the detector concept, its integration in PX56, the expected background, and projected sensitivities for several LLP benchmark models produced through Higgs, heavy-flavour, and electroweak processes. With 3 ab-1 of data at the HL-LHC, GRENDEL achieves leading sensitivity for LLPs with masses from 1-55 GeV (reaching sensitivity to Higgs decay branching ratios below 2x10⁻⁵ for 40 GeV LLPs). The GRENDEL detector will be documented in a paper soon to be released on arXiv.

        Speakers: Federico Leo Redi (U. of Bergamo and INFN Milan (IT)), Matthew Daniel Citron (University of California Davis (US))
        ws_LLP2026_GRENDEL_260630.pdf
      • 37
        CODEX-β: From Installation to Data Taking, Hardware and Software Integration

        CODEX-b (COmpact DEtector for EXotics at LHCb) is a proposed transverse detector designed to search for Beyond the Standard Model (BSM) physics, targeting Long-Lived Particles (LLPs) with displaced decays. It would consist of a 10 × 10 × 10 m³ array of Resistive Plate Chamber (RPC) triplet units located in the LHCb cavern, enabling access to parameter space beyond the reach of existing experiments. This work presents the final hardware installation and software integration of the technological demonstrator CODEX-β, a 2 × 2 × 2 m³ RPC-based array designed to validate the detector’s feasibility and characterize expected backgrounds in the LHCb environment. A dedicated fast-simulation framework and a tailored event model have been developed for the project. Furthermore, GPU-based reconstruction algorithms for HLT1 and various HLT2 selections have been implemented to enable efficient detector operation within LHCb. These developments validate the CODEX-b technology and demonstrate its potential for successful integration and operational viability in the future.

        Speaker: Alberto Martinez Armas (Universidade de Santiago de Compostela (ES))
        CODEX_LLP2026.pdf
      • 38
        Axion-like Particle Searches with the FASER Detector at the LHC: Reach and Prospects

        The FASER detector at the LHC is a small, far-forward detector 480 m from the ATLAS IP1 that is capable of probing numerous BSM physics models. This talk presents the re-interpretation of FASER's 2024 search for axion-like particles (ALPs) with the addition of the 2024 Run 3 dataset. This search probes models including ALPs with coupling to the $SU(2)_L$ gauge boson, the PBC benchmark ALPs with coupling to photons, and a novel model which uses the LHC as a Light Shining through Wall experiment. The increased luminosity and development in signal selection improves sensitivity in previously unprobed regions of parameter space. Additional models that have similar decay signatures to the ALPs are also explored as well as future prospects of FASER and its planned upgrades.

        Speaker: Charlotte Cavanagh (ETH Zurich (CH))
        Lottie_LLP_2026_talk.pdf
    • Wednesday 1 July
      • 39
        New physics searches in beam dump at the NA62 experiment

        The NA62 experiment at CERN, designed to measure the highly-suppressed decay $K^{+} \to \pi^{+}\nu\bar{\nu}$, has the capability to collect data in a beam-dump mode, where 400 GeV protons are dumped on an absorber. In this configuration, New Physics particles may be produced in the absorber and decay in an instrumented volume beginning approximately 80 m downstream of the dump. Preliminary results from a search for Heavy-Neutral leptons decaying in flight to semi-leptonic final states are reported, based on an analysis of a sample of $6.2 \times 10^{17}$ protons on dump collected in 2021, 2023, and 2024.

        Speaker: Stefan Alexandru Ghinescu
        LLP_2026_Ghinescu.pdf
      • 40
        Search for stau pair production with the DisTau identification algorithm

        This talk presents a recent result from the CMS Collaboration: the search for long-lived supersymmetric partners of the tau leptons decaying within the tracker volume of the CMS experiment. The search was performed by analyzing an integrated luminosity of 138 fb-1 collected by the CMS experiment between 2016 and 2018 using a dedicated identification algorithm targeting tau lepton decays displaced from the primary interaction vertex: DisTau. The search extends the explored parameter space for supersymmetric models and improves limits compared to previous searches. This talk will provide an overview of the search strategy, with the DisTau algorithm being highlighted for its contribution in improving the sensitivity to these exotic detector signatures, and show the improved limits on the proper lifetime and mass of the tau super-partner in gauge-mediated supersymmetry-breaking models.

        Speaker: Andrea Cardini (ICTEA - Universidad de Oviedo (ES))
        AndreaCardini-StausSearch.pdf
      • 41
        New Strategies for Long-Lived Heavy Neutral Leptons in the $\ell+\rho$ Channel

        Heavy Neutral Leptons (HNLs) in the GeV mass range can give rise to long-lived signatures and observable effects across a range of experiments, such as ATLAS and SHiP. Their phenomenology depends on both production and decay dynamics, motivating the development of robust and broadly applicable analysis strategies.

        In this talk, I present recent progress in developing such strategies for semileptonic HNL decays in the $\ell+\rho$ channel, with $\rho \to \pi^\pm \pi^0$. Kinematic reconstruction techniques based on mass constraints allow partial recovery of missing information associated with the $\pi^0$, while polarization and angular observables, provide powerful discriminants of the production mechanism and the nature of the HNL.

        These methods are demonstrated within modern simulation frameworks, enabling a consistent treatment of kinematics and spin correlations.

        Speaker: Marzieh Bahmani (Humboldt University of Berlin (DE))
        HNL_llp26_v02.pdf
      • 42
        Recent searches for new LLPs using the MicroBooNE detector

        The intense meson fluxes produced in conventional neutrino beamlines provide a rich test bed for probing long-lived particles beyond the Standard Model. MicroBooNE, a liquid argon time projection chamber at Fermilab, is uniquely positioned for such searches, operating both off-axis to the Main Injector Neutrino (NuMI) beamline and on-axis to the Booster Neutrino Beam (BNB).

        In this talk, I will present two searches that exploit decays of the NuMI kaon flux to constrain dark-sector models. First, I will describe our recent search for higgs portal scalars decaying to electron–positron pairs, which set the strongest experimental limits for scalar masses between 110 and 155 MeV. I will then discuss our most recent search for heavy neutral leptons, targeting both electron–positron and neutral pion visible final states. This analysis has already achieved world-leading constraints on sterile neutrino masses between 35 and 175 MeV, but I will go further by outlining ongoing efforts to maximise sensitivity using the full MicroBooNE dataset and improved analysis techniques.

        Speaker: Magnus Handley (University of Cambridge)
        MicroBooNE_LLP_2026.pdf
      • 43
        Long-Lived Particle Signatures in Nucleon Decay

        We present a new class of nucelon decay signatures including a long-lived particle (LLP) as a decay product. Therefore, the detector signature consists of two spatially separated but temporally correlated vertices, the initial nucleon decay and the decay of the LLP. The signature has the advantage to be nearly background-free in experiments such as Super-Kamiokande, Hyper-Kamiokande and JUNO, and hence, motivates further analysis. We discuss the case of vector LLPs in the framework of effective field theory and estimate experimental sensitivities.

        Speaker: Patrick Adolf
        LLP_PA.pdf
      • 44
        Search for emerging jets in $pp$ collisions at $\sqrt{s} = 13~\mathrm{TeV}$ with the ATLAS experiment

        A search is presented for emerging jets using $140~\mathrm{fb}^{-1}$ of proton--proton collision data at $\sqrt{s} = 13~\mathrm{TeV}$, collected by the ATLAS experiment between 2015 and 2018. The search looks for the existence of a dark sector with symmetries similar to those in quantum chromodynamics. This dark sector is populated with dark quarks, which undergo showering similar to quarks in the Standard Model, leading to a high multiplicity of long-lived dark hadrons within a dark jet. These dark hadrons subsequently decay to Standard Model particles via a new heavy scalar mediating particle $\phi$. This results in jets which contain multiple displaced vertices, known as emerging jets. This analysis targets four-jet topologies, with two emerging jets and two Standard Model jets, resulting from the decay of pair-produced scalar mediators. No significant excess above the Standard Model background is observed. For dark pion proper decay lengths of $20~\mathrm{mm}$, mediator masses are excluded between $1~\mathrm{TeV}$ and $2~\mathrm{TeV}$ assuming a dark pion mass of $20~\mathrm{GeV}$.

        Speaker: Ian Alejandro Ramirez-Berend (Carleton University (CA))
        LLP_Workshop_IRB_1July26.pdf
      • 10:50
        Coffee/Tea Break
      • 45
        Search for Quirks with the FASER Experiment at the LHC

        Quirks are particles that have Standard Model (SM) interactions and also interact through infracolor (IC), a new strong force. In models where the IC confinement scale is much less than the quirk mass, $\Lambda \ll m_\mathrm{Q}$, quirk pairs produced at colliders are connected by an IC string force and oscillate around their center of mass with unusual trajectories that escape traditional particle searches. We present a search for quirks using data collected in 2022-2024 by the FASER detector at the CERN Large Hadron Collider. The analysis is based on an integrated luminosity of $186~\mathrm{fb}^{-1}$ of proton--proton collisions at a center-of-mass energy of $\sqrt{s} = 13.6~$TeV. This analysis constitutes the first search for quirks with masses above the weak scale for this broad range of $\Lambda$ and demonstrates the potential of FASER and other forward experiments to discover not only light and feebly-interacting particles, but also new particles with weak-scale masses and unconventional signatures.

        Speaker: Arash Jofrehei (Universite de Geneve (CH))
        LLP2026_FASER_Quirks.pdf
      • 46
        Search for dark photon bremsstrahlung by muons in proton-proton collisions using the CMS detector

        A recent analysis for dark photon bremsstrahlung using data collected by the CMS detector at the LHC is presented. The search uses the tag-and-probe method with muon-antimuon pairs produced in the decay of Z-bosons to search for secondary interactions in the calorimeters, using one fully reconstructed muon to trigger and tag the event and using the inner detector track of the other muon to search for secondary interactions in the calorimeters. The analysis targets secondary interactions where significant energy is carried by invisible particles, where either no muons are reconstructed near the track or muons are reconstructed with significantly altered trajectories. Limits are placed in the two dimensional plane of the square of the dark photon mixing parameter ϵ2 and the dark photon mass for A' masses in the range 10 MeV to 1 GeV. This is the first search of this type at an LHC experiment.

        Speaker: Michael Revering (University of Cambridge (GB))
        disappMu_llpWorkshop_.26_7_1.pdf
      • 47
        Searching for apparent baryon number violation in $\Lambda_c^+$ decays at the Super Tau-Charm Facility

        Observation of baryon number violation (BNV) in laboratory experiments would constitute unambiguous evidence for physics beyond the Standard Model. We propose dedicated searches for \textit{apparent} BNV in charm-baryon decays, $\Lambda_c^+\to M^+ +$~missing energy ($M=\pi, K$) where the missing energy stems from a resonance. These channels have not been explored experimentally so far, despite the relatively clean environment potentially provided by near $\Lambda_c^+\overline{\Lambda}_c^-$ threshold production at $e^+e^-$ colliders. Performing state-of-the-art Monte Carlo simulations for the proposed Super Tau-Charm Facility (STCF), we evaluate the signal efficiencies and derive projected model-independent sensitivities under the assumption of negligible background. We further interpret these sensitivities within two theoretical frameworks: a sterile-neutrino-extended low-energy effective field theory ($\nu$LEFT) and R-parity-violating (RPV) supersymmetry. With an integrated luminosity of 1~ab$^{-1}$, STCF can probe new-physics scales of several TeV in the $\nu$LEFT description and constrain the RPV model parameter $\lambda''_{212}/m^2_{\tilde{q}}$ down to about $0.1~\mathrm{TeV}^{-2}$. Our results demonstrate that STCF provides a highly competitive opportunity for probing BNV interactions in rare charm-baryon decays.

        Speaker: Zeren Simon Wang (Hefei University of Technology)
        BNV_Lambdac_decay.pdf
      • 48
        Dedicated LLP Detector Concepts for Future Colliders: DELIGHT-SHIELD, DELIGHT and FOREHUNT

        Searches for new physics increasingly focus on light, weakly interacting long-lived particles (LLPs), where highly displaced signatures challenge general-purpose detectors. Dedicated LLP experiments are therefore essential, but their impact depends critically on optimised geometry and placement. The Future Circular Collider (FCC) offers a unique opportunity to design such detectors from the outset. We first explore a shielding-based detector concept, DELIGHT-SHIELD, at a dedicated interaction point for FCC-hh, with alternative options for a staged implementation. We next discuss two complementary dedicated detector concepts: DELIGHT, a transverse detector with a shared design for both FCC-ee and FCC-hh runs, and FOREHUNT, a forward detector targeting boosted LLP signatures in the forward direction. We present sensitivity projections, discuss key background sources, show realistic background estimates using a full detector simulation using Geant4, and discuss their mitigation in order to assess the feasibility of these designs for improving the coverage of previously unexplored LLP parameter space.

        Speaker: Rhitaja Sengupta (BCTP and Physikalisches Institut der Universität Bonn, Germany)
        rhitaja_LLP_workshop_2026.pdf
      • 12:30
        Lunch
      • 49
        PREFACE: A new very forward long-lived particle search at the LHC

        PREFACE is being proposed as a new CMS subsystem in the very forward direction at z = 100-120m, with silicon tracking and HGCAL modules mounted above the beam pipe. It has unique sensitivity in regions of the mass:coupling plane to any BSM weakly interacting particles that can pass through > 30 m of iron and decay to SM particles in a 10 m^3 fiducial volume. Possibilities include dark scalars, HNLs. ALPs, dark photons, etc. PREFACE does not require any changes to the LHC infrastructure and could begin in Run 4.

        Speaker: Dr Aldo Penzo (Univ. Iowa)
        PREFACE-LLP2026_01-07-2026.pdf
      • 51
        Search for Inelastic Dark Matter with Soft Displaced Electrons at the CMS Experiment

        This talk presents a new search for inelastic dark matter (IDM) in the dielectron final state with the CMS detector. IDM posits a dark photon portal to dark sector states with a small mass imbalance, with one acquiring a macroscopic lifetime resulting in a distinct LHC final state with soft, displaced leptons and large missing transverse momentum. We use a special electron reconstruction algorithm that improves reconstruction efficiency at low transverse momentum and high displacement by relying on tracker-based seeding. The search probes dark matter scenarios with mean proper lifetime between 1 and 1000mm, complementing and extending limits from other IDM searches from direct and indirect detection experiments.

        Speaker: Kyungmin Park (Carnegie-Mellon University (US))
        iDMe_LLP2026_KyungminPark_20260701.pdf
      • 52
        ANUBIS: latest results and Physics Case

        The Standard Model (SM), despite its successes, is known to have several major limitations, such as the inability to describe Dark Matter, which has been astronomically observed. These limitations have led to the development of a variety of Beyond the Standard Model (BSM) theories to resolve them, which can often give rise to Long-Lived Particles (LLPs). LLPs provide a valuable probe of BSM models, so the ANUBIS experiment was proposed as a dedicated LLP experiment transverse to the beamline at ATLAS to explore regions of parameter space not previously covered by any existing experiments. A prototype detector, proANUBIS, operated for two years in the ATLAS cavern, accumulating around 176.3 fb^-1 of pp data. The first study of the proANUBIS dataset focused on searching slow muons, β>0.8, by synchronisation with ATLAS data as an excellent proof of concept of the possibilities of a symbiotic relationship between ANUBIS and ATLAS. Additionally, updated sensitivities to Heavy Neutral Leptons (HNLs) and Axion-Like Particles (ALPs), as well as the ongoing development of the SET-ANUBIS Sensitivity studies framework, are highlighted.

        Speaker: Aashaq Shah (University of Cambridge (GB))
        anubis_LLP2026.pdf
      • 53
        The MoEDAL-MAPP Programme at LHC’s IP8 – Current Status and Future Plans

        The MoEDAL-MAPP programme at LHC Interaction Point 8 provides a distinctive approach to search for long-lived and feebly interacting particles, using both the MoEDAL highly ionizing particle (HIP) detector and the MAPP apparatus in the UA83 tunnel. In Run 3, MoEDAL has continued searches for magnetic monopoles, highly electrically charged objects, and other slowly moving highly ionizing states, while MAPP-1 has been developed to extend sensitivity to milli-charged and other weakly ionizing particles through a dedicated scintillator-based detector system.This talk will review the current end-of-Run-3 status of MoEDAL-MAPP, including detector operation, MAPP-1 commissioning, DAQ readiness, background studies, calibration work, and near-term physics prospects. Particular attention will be given to lessons learned during installation and commissioning, and to their implications for future physics data-taking. The presentation will also discuss realistic prospects for LS3 and Run 4, including the proposed Outrigger detector, intended to enhance acceptance for higher-mass milli-charged particles and related signatures. MAPP-2, a longer-term detector concept aimed at improving sensitivity to neutral long-lived particles in the HL-LHC era, will be mentioned briefly in the context of ongoing studies, remembering that it is subject to approval, resources, manpower, and the appropriate CERN review processes. By combining passive HIP detection with dedicated scintillator systems for feebly interacting particles, MoEDAL-MAPP offers a complementary contribution to the continuingLHC programme.

        Speaker: James Pinfold (University of Alberta (CA))
        LLP2026.pdf
      • 15:30
        Coffee/Tea Break
      • Free Time: Explore Cambridge
        LLP2026 Tours + Dinner
      • Dinner Cloister Court (Sidney Sussex College (https://maps.app.goo.gl/jdVT6kqegxcLsbDi7))

        Cloister Court

        Sidney Sussex College (https://maps.app.goo.gl/jdVT6kqegxcLsbDi7)

        Sidney St, Cambridge CB2 3HU, United Kingdom https://maps.app.goo.gl/jdVT6kqegxcLsbDi7
        2026_06_29_LLPWS2026_dinner.pdf
        Maps location
        Sidney Sussex College
        • 54
          Drinks Reception
        • 55
          Dinner
    • Thursday 2 July
      • 56
        Long-Lived Particles from Strongly Interacting Dark Sectors

        Strongly-interacting dark sectors often contain a wide variety of long-lived particles. In this talk I'll provide an overview of the physics, what strong-coupling "buys" you in terms of the effective theory of the low energy degrees of freedom, and then survey the theory landscape. Among the most promising targets for current and future experiments are dark glueballs and dark mesons that have a wide range of lifetimes and decay topologies.

        Speaker: Graham Kribs
        cambridge_llp_2026_07.pdf
      • 57
        Search for massive, long-lived particles with displaced vertices and displaced muons using ATLAS 2022-2024 Data

        A new search for massive long-lived particles (LLPs) is presented using 164 fb⁻¹ of proton-proton data at √s = 13.6 TeV collected by the ATLAS detector during 2022–2024, targeting events with displaced vertices and displaced muons (arXiv:2603.01991). It leverages improved Large Radius Tracking and displaced muon triggering capabilities introduced for Run 3. Background contributions are estimated using fully data-driven techniques, and no significant excess above the expected background is observed. Upper limits at 95% confidence level are set on the visible cross-section of one displaced vertex and one displaced muon on the order of 0.01 fb. World-leading limits are also set on the production cross-sections of several lepton-number-violating and baryon-number-violating benchmark models of R-parity-violating supersymmetry.

        Speaker: Laura Elaine Bruce (Harvard University (US))
        labruce_LLP2026.pdf
      • 58
        MATHUSLA: Progress and Updates

        MATHUSLA (MAssive Timing Hodoscope for Ultra-Stable neutraL pArticles) is a proposed long live particle detector to be installed on the surface above the CMS collision point at the LHC. The large area footprint of 40 m x 40 m x 25 m, as described in the Conceptual Design Report published in 2025[1], combined with the distance of $\sim$100 m from the collision point gives MATHUSLA an order of magnitude more sensitivity to LLPs with lifetimes between 10-10000 m compared to the LHC detectors. The modular design in MATHUSLA would allow for operation to begin immediately with the installation of one 9 m x 9 m tower and seamlessly integrate additional modules as the detector is constructed. This talk will cover recent progress on the development of trigger algorithms, background studies, and prototype detector results from the University of Victoria and the University of Toronto.
        [1] https://arxiv.org/abs/2503.20893

        Speaker: Caleb Miller
        Mathusla_LLP_Cambridge.pdf
      • 10:45
        Coffee/Tea Break
      • 59
        Testing frozen-in dark matter with a long-lived dark Higgs

        I will motivate the quest for new, long-lived physics at colliders able to explain dark matter. The impact of the cosmic reheating dynamics on dark matter freeze-in production will be discussed in a specific Higgs-portal model that predicts a long-lived dark Higgs boson. I will emphasise the crucial role of collider LLP searches, focusing on prospects at the Future Circular Collider (FCC-hh) to unveil new dark sector physics.

        Speaker: Giovanna Cottin (Pontificia Universidad Católica de Chile (CL))
        LLP2026_GCOTTIN.pdf
      • 60
        Search for long-lived heavy neutral leptons in proton-proton collisions with one prompt muon and a secondary vertex from two displaced muons

        This talk presents a search for heavy neutral leptons (HNLs) in final states with three muons, with one originating from the prompt primary interaction vertex and the other two originating from a common displaced vertex. The analysis strategy is optimised for large HNL decay lengths by considering very displaced muons reconstructed only outside the tracker of the CMS experiment at the CERN LHC. This enhances the analysis reach in the high HNL lifetime region, corresponding to low HNL masses and small mixing with standard model neutrinos, where prompt and tracker-based displaced analyses have limited acceptance. The analysed proton-proton collision data correspond to integrated luminosities of 138/fb recorded at a centre-of-mass energy of 13 TeV between 2016 and 2018, and of 34.6/fb recorded at 13.6 TeV in 2022.

        Speaker: Anna Mascellani (ETH Zurich (CH))
        LLP2026_HNLdisplacedMu.pdf
      • 61
        Quantum Number Theory and New Predictions of Millicharge Doublet

        In quantum gauge theories, anomaly cancellation severely restricts the allowed patterns of chiral charges. Here we show that, in a phenomenologically motivated framework for light minicharged particles, the anomaly cancellation conditions are equivalent to the degree k=3 Prouhet-Tarry-Escott problem in number theory. This correspondence immediately implies that the hidden sector must contain at least four minicharged states. For constructions based on minimal ideal solutions, the mass spectrum generically exhibits a near-degenerate doublet structure, so that the discovery of one minicharged particle would point to a partner state with the same minicharge and a nearby mass. Our results uncover an unexpected link between quantum consistency and number theory, with direct implications for model building and future searches.

        This talk is based on https://arxiv.org/abs/2603.12320

        Speaker: Yu-Dai Tsai (The University of Manchester)
        Cambridge_Tsai26.pdf
      • 62
        DarkMatterLive: A Community Framework for unified dark sector costraints including the ones with LLPs.

        In many BSM scenarios, dark matter candidates manifest as long-lived particles (LLPs), arising from suppressed couplings or small mass splittings. These scenarios are probed through LLP searches at colliders and fixed-target experiments, complemented by dark matter constraints from direct, indirect, and cosmological observations. However, results across these programmes are reported in heterogeneous parameterisations, such as cross-sections, event rates, lifetimes, branching fractions, or model-dependent couplings (e.g. kinetic mixing or portal interactions), complicating reinterpretation and consistent global constraints.

        DarkMatterLive is a collaborative framework for building and sharing interactive visualisations of dark matter constraints, including LLP and dark sector models, based on published experimental and observational results. It brings together limits that are otherwise difficult to compare, reinterpreting and renormalising them in a consistent, model-aware parameter space. Where possible, constraints are recast in standard coupling-mass-lifetime variables following widely used conventions, such as the Beyond Collider benchmarks, while preserving clear links to the original sources, assumptions, and caveats.

        The platform already supports LLP use-cases such as dark photon , where constraints on kinetic mixing are mapped into lifetime-mass space relevant for displaced signatures. Hosted on CERN PaaS cloud infrastructure, it is publicly available through the https://darkmatter.web.cern.ch/ web interface, with a citable release archived as 10.5281/zenodo.18135859. It also connects to community resources such as the HEPData portal, helping organise new inputs within a transparent review workflow.

        To make contributions easier, DarkMatterLive provides a data-ingestion workflow based on CSV curve data and JSON metadata. It supports contributions from multiple communities, where new results and key reinterpretation and renormalisation factors are documented and peer-reviewed through GitHub pull requests or CERN GitLab merge requests before inclusion. Code and datasets are openly maintained, supporting transparency and shared ownership. Additional AI-MCP-based ingestion modules are being integrated into platform workflows.

        Speaker: Dr Brij Kishor Jashal (Rutherford Appleton Laboratory)
        Brij_02-07-2026-DMlive.pdf
      • 63
        Looking forward to LLP 2027!
        Looking_foward_to_LLP_2027.pdf
      • 12:35
        Lunch
      • Hands-on Session: Session 3
        Hackathon Materials
      • 15:00
        Coffee/Tea Break
      • Hands-on Session: Session 4
        Hackathon Materials
    • Friday 3 July
      • 65
        Long-lived HNLs via ALP portal at the LHC

        Heavy neutral leptons (HNLs) and axion-like particles (ALPs) are both considered well-motivated candidates for beyond the standard model (BSM) physics. If ALPs with sizable couplings to gluons (and HNLs) exist, they will be abundantly produced at the LHC, possibly providing high sensitivities to HNL parameters. We study the prospects for the high-luminosity LHC to search for long-lived HNLs in such a scenario, considering future far detectors as well as ATLAS in our calculations.

        Speaker: MARTIN KONRAD HIRSCH Not Supplied (Instituto de Física Corpuscular, Universidad de Valencia - CSIC)
        MH_LLP26.pdf
      • 66
        Search for displaced muons in proton-proton collisions using the CMS Experiment

        This talk presents recent results from searches for displaced dimuon resonances with the CMS detector, targeting a broad range of new physics scenarios involving long-lived particles. The most recent results, obtained with scouting streams, are compared with other existing CMS searches, highlighting their complementarity at lower masses. Signatures with one or multiple dimuon resonances over a wide range of lifetimes are probed, spanning lifetimes from 0.1 to 100 cm, while diverse displaced topologies are explored. The results illustrate how different analysis strategies and data-taking approaches enable effective coverage of the phase space, extending the reach to low transverse momentum regimes and very low masses, and providing sensitivity to a variety of theoretical models.

        Speaker: Celia Fernandez Madrazo (Boston University (US))
        CFM_LLP2026-4.pdf
      • 67
        Prospects for the search of quirks at LHCb

        Quirks are heavy particles connected by a flux tube from a hidden confining force that remain weakly constrained in large regions of their parameter space. This flux tube acts as a string that, at short enough distance, stretches as the quirk pair separates, then pulls the pair back together leading to interesting dynamics. We propose a novel search using the LHCb Vertex Locator (VELO), whose forward geometry and software-based trigger are uniquely suited to detecting the characteristic back-to-back, planar hit patterns produced by quirk pairs with little transverse recoil. Using detailed simulations of the VELO geometry, together with simple geometric selections, we present different sensitivity projections, demonstrating that LHCb can probe parameter regions inaccessible to existing ATLAS and CMS searches and offering a powerful, complementary path toward discovering quirks.

        Speaker: Alejandro Novo Cal (Universidade de Santiago de Compostela (ES))
        Quirks_LLP2026.pdf
      • 68
        LLP opportunities at 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 $O(6\cdot10^{12})$ Z boson decays are expected. The large additional data samples of Higgs bosons, W bosons, and top quarks in very clean experimental conditions will offer extra opportunities for discoveries at higher 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: Mahmoud AlThakeel (Universita Di Bologna (IT))
        Mahmoud_LLPs_at_FCC-ee.pdf
      • 69
        Searches for long-lived particles decaying in the CMS muon detector system

        Many extensions of the Standard Model predict new long-lived particles (LLPS) with a wide range of possible proper lifetimes, masses and decay modes.

        This talk presents recent results for searches for long-lived particles decaying inside the CMS muon detector system. The focus will be on the most recent results obtained with proton-proton collisions recorded during LHC Run 3, corresponding to an integrated luminosity of 170 1/fb. The CMS muon detector system consists of gaseous detectors interleaved with layers of steel of the magnetic flux-return yoke. Long-lived particles decaying within the steel can induce electromagnetic and hadronic showers which can be reconstructed as high multiplicity hit clusters, effectively interpreting the muon detector system as a sampling calorimeter. This so-called muon detector shower (MDS) signature is therefore sensitive to various LLP decay modes, including decays to hadrons and taus. The MDS are furthermore only sensitive to the energies of the LLPs, not their mass, allowing searches to reach high sensitivity independent of the LLP mass. In addition, the detector material and steel in front of and in between the muon detectors provides effective shielding against many sources of background that would affect searches in the inner parts of the CMS detector. Dedicated triggers have been developed and successfully deployed to record events with this unique MDS signature during LHC Run 3. Analyses by the CMS Collaboration using the MDS signature include not only searches for LLPs over a wide range of masses, but also searches for heavy-neutral leptons.

        Speaker: Karim El Morabit (Hamburg University (DE))
        MDS_Searches_CMS_LLP2026.pdf
      • 10:30
        Coffee/Tea Break
      • 70
        Same-sign dimuon probe of charged lepton flavor violation at electron–photon colliders

        Observation of charged lepton flavor violation would constitute unambiguous evidence for physics beyond the Standard Model (SM). We identify a previously unexplored same-sign dimuon signature in electron--photon collisions, $\gamma e^- \to e^+\mu^-\mu^-$, mediated by an axionlike particle (ALP) with flavor-violating $e$--$\mu$ couplings. The absence of irreducible SM backgrounds and the on-shell production of the ALP render this channel intrinsically clean and highly sensitive, with only small residual backgrounds arising from detector effects. Such collisions can be realized via laser Compton backscattering at $e^+e^-$ colliders including BEPC-II with the BESIII detector, STCF, and ILC. We find that STCF and ILC can probe couplings one to two orders of magnitude below existing bounds. This combination of resonant production, vanishing irreducible background, and same-sign topology would be difficult to achieve in conventional $e^+e^-$ or hadron-collider environments, establishing electron--photon collisions as a uniquely powerful probe of charged lepton flavor violation.

        Speaker: Dr Yu Zhang (Hefei University of Technology)
        Same sign muon pair at egamma colliders@LLP26.pdf
      • 71
        Search for long-lived charged particles using level-1 scouting data from proton-proton collisions at the CMS experiment

        The recent search at the CMS experiment for Long-Lived Charged Particles in the low beta region is presented. The search utilizes the capabilities introduced by the deployment of the CMS Level-1 Data Scouting System in Run 3, which allows for the collection of muon barrel system information from consecutive bunch crossings, without the application of any triggers. This novel approach exhibits high sensitivity in the $\beta<0.5$ region of phase-space, which is practically inaccessible to conventional dE/dx searches, due to limitations introduced by triggering.

        The results obtained with 2024 CMS data from proton-proton collisions at $\sqrt{s}=13.6 \; TeV$ and corresponding to an integrated luminosity of $3.7 \; fb^{-1}$ are presented in this talk. They are interpreted in terms of cross-section limits to several theoretical models giving rise to Heavy Stable Charged Particles. In addition, the ongoing effort to extend the analysis to the full Run 3 L1 scouting dataset is described, along with perspectives for the High-Luminosity LHC.

        Speaker: Elton Shumka (Purdue University Northwest (US))
        LLP_2026_presentation_HSCP_search_CMS.pdf
      • 72
        Model-independent searches for long-lived particles at LHCb with BuSca

        BuSca (Buffer Scanner) is a real-time data monitoring and analysis framework designed to guide searches for new physics at the LHCb experiment at CERN, operating prior to any trigger decision. By accessing the full proton–proton collision rate of 30 MHz, it enables the exploration of previously inaccessible regions of phase space. Long-lived particle tracks are reconstructed and analysed in real time using highly GPU-optimized software in a model-independent approach. Preliminary results from Run 3 data corresponding to more than 15/fb are presented, together with ongoing developments of this framework and prospects for Run 4.

        Speaker: Jiahui Zhuo (Univ. of Valencia and CSIC (ES))
        LLP 2026 BUSCA Final.pdf
      • 73
        Closeout + prize winners!
      • Departure