LLP2024: Fourteenth workshop of the Long-Lived Particle Community

1 Jul 2024, 08:00 → 5 Jul 2024, 22:00 Asia/Tokyo

University of Tokyo

James Beacham (Duke University (US)), Ryu Sawada (University of Tokyo (JP))

Short url: https://indico.cern.ch/e/LLP_July_2024

-------------- LLP2024 --------------

The fourteenth workshop of the Long-Lived Particle Community will occur from 1 to 5 July, 2024, at the University of Tokyo, Hongo area which is located in the center of Tokyo city.

This will be the first LLP Community workshop outside of Europe! Please register and submit an abstract, if you have one.

Previous workshops can be found here.

Main venue is Koshiba Hall. Details can be found at this page.

A reminder of the CERN code of conduct: "Be excellent to each other".

Organizers:

Carlos Vazquez Sierra
Masahiro Morinaga
Sai Neha Santpur
Osamu Jinnouchi
James Beacham
Natsumi Nagata
Matthew Citron
Andrii Usachov
Mason Proffitt
Audrey Kvam
Ryu Sawada
Lisa Benato
Satoshi Shirai
Hideyuki Oide
Margaret Lutz
Juliette Alimena
Albert De Roeck
Hidetoshi Otono
Federico Leo Redi
José Francisco Zurita

The workshop is supported by ICEPP, WPI/IPMU (20H05860) and JSPS-KAKENHI.

  

dinner_LLP2024.pdf

group_photo.JPG

LLP2024_Tokyo_Poster_Ohara.pdf

Monday 1 July

09:00 → 09:30 Logistics: Registration

09:30 → 10:00 Logistics: Introduction

09:30 Welcome from the University of Tokyo

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

Welcome_LLP2024.pdf

09:40 Introduction to the Long-Lived Particle Community

Speaker: James Beacham (Duke University (US))

Beacham_LLP_Fourteenth_Community_Workshop_Intro_Tokyo_2024Jul1.pdf

09:50 Logistics and contents of the LLP2024 edition

Speakers: Carlos Vazquez Sierra (Universidade de Santiago de Compostela (ES)), Ryu Sawada (University of Tokyo (JP))

LLP24_CVS.pdf

logistics_LLP2024.pdf

10:00 → 11:30 Overviews: CMS, ATLAS and LHCb

10:00 Overview of ATLAS results

Speaker: Hideyuki Oide (KEK (JP))

LLP2024_ATLAS_Overview.pdf

10:30 Overview of CMS results

Speaker: Andre Frankenthal (Princeton University (US))

Frankenthal_CMSLLP_July2024.pdf

11:00 Overview of LHCb results

Speaker: Andrii Usachov (Nikhef and VU (NL))

ausachov_LHCb_LLP14.pdf

11:30 → 11:50 Breaks: Coffee break

11:50 → 12:50 Overviews: Belle-II and BES-III

11:50 Overview of BES-III results

Speaker: Yu Zhang (University of South China)

OverviewofBESIII1.pdf

12:20 Searches for dark sector particles at Belle and Belle II

The Belle and Belle~II experiment have collected samples of $e^+e^-$ collision data at centre-of-mass energies near the $\Upsilon(nS)$ resonances. These data have constrained kinematics and low multiplicity which allow searches for new long-lived particles in the mass range from a few MeV to 10~GeV. Belle II has searched for a long-lived scalar particle $S$ produced in $B\to KS$ decays using $189~\mathrm{fb}^{-1}$ of data. Using tau-lepton decays in a 915~fb$^{-1}$ sample, Belle has searched for a long-lived heavy neutral lepton that mixes primarily with the tau neutrino.

Speaker: Ori Fogel (Tel Aviv University)

LLP0724_Belle.pdf

12:50 → 13:00 Logistics: Workshop picture

13:00 → 14:30 Breaks: Lunch

14:30 → 15:50 Dedicated or uniquely-sensitive long-lived particle detectors

14:30 COmpact DEtector for EXotics at LHCb: CODEX-b

CODEX-b, the COmpact DEtector for EXotics at LHCb, is a proposed particle detector for exotic long-lived particles (LLPs). These LLPs are potential candidates for dark sector portals, and so the observation of LLPs could unlock unexplored physics scenarios. Planned for installation near LHC interaction point 8, CODEX-b leverages fast resistive plate chambers (RPCs) with excellent temporal and spatial resolution. CODEX-b is sensitive to a wide range of new physics scenarios due to near zero-background environment which can be achieved with a fully hermetic structure and active shielding. A proof-of-concept demonstrator, CODEX-beta, is under construction, with data taking planned for late 2024 and 2025. CODEX-beta serves as a crucial validation platform for background measurements, integration with LHCb readout, and assessment of tracking and mechanical support systems.

Speakers: Jake Pfaller, Jake Pfaller (University of Cincinnati (US))

Pfaller_LLP2024.pdf

14:50 SUBMET

Speaker: Mr Hoyong Jeong (Korea University (KR))

LLP2024_HY.pdf

15:10 MATHUSLA

Speaker: Erez Etzion (Tel Aviv University (IL))

LLP2024-MATHUSLA-Etzion.pdf

15:30 ANUBIS: Initial commissioning results from proANUBIS

New long-lived particles (LLPs) are a class of particles that are generically predicted in various theoretical extensions of the Standard Model such as those with Dark Matter candidates. The LHC has a detailed programme to search for LLPs produced at energies at the electroweak scale and above, which has mostly been focused on ‘prompt’ decays within the LHC experiments. In contrast, the ANUBIS experiment has been proposed to exploit the available space in the ATLAS cavern to search for LLPs with decay lengths of O(10m) and above. To do so the ceiling and bottom of the service shafts above the ATLAS experiment will be instrumented with tracking stations. This talk will outline the ANUBIS project, and its physics case before detailing the design, installation and commissioning of a completed prototype detector, proANUBIS, and a recent upgrade made to its trigger system. Additionally, an initial look at the 2024 commissioning data will be given, showing the ongoing progress and future plans for the experiment.

Speakers: Michael Revering, Michael Revering (University of Cambridge (GB))

anubisCommissioning_LLP2024.pdf

15:50 → 16:20 Breaks: Coffee break

16:20 → 17:40 Theory and phenomenology

16:20 Simplified t-channel dark matter models and long-lived particles

Simplified t-channel dark matter models with coloured mediators are rich in phenomenology and can be mapped to a variety of UV complete scenarios.
In this talk, I will discuss the degenerate mass region of mediator and dark matter states, discuss the rich phenomenology including Sommerfeld enhancement and bound state information in opening new parameter space. I discuss the collider implications and bounds originating from long-lived particle searches, including the powerful impact of heavy stable charged particle searches in constraining the parameter space. I will also discuss the potential of long-lived particle searches to constrain this parameter space at Hl-LHC, as well as potential experiments such as FASER.

Speaker: Dipan Sengupta (University of New South Wales, Sydney, Australia)

LLP_Tokyo_Dipan.pdf

16:40 Dark Showers with the Z-portal

We study dark shower signals from a dark QCD sector, with the Z boson being the main portal between the Standard Model and the dark QCD sector. It can be achieved by integrating out heavy electroweak doublet dark quarks or from the mixing between the Z boson and a dark Z' coupling to the dark quarks. The lightest dark hadrons are assumed to be GeV-scale dark pions. The dark pions decays mediated by the Z boson typically have decay lengths in the range of 1 mm to 10 m. We show that the current displaced di-muon resonance searches at CMS and LHCb can be recasted for the dark showers searches from the Z decay and dark pion searches from FCNC B meson decays, probing parameter regions beyond the bounds from the electroweak precision measurements and other indirect constraints. Future reaches at the LHC, including auxiliary detectors (FASER, Codex-b, MATHUSLA) and other experiments will be discussed.

Speaker: Hsin-Chia Cheng

dark_shower_LLP.pdf

17:00 Confining Dark Sector and Long-lived Particle Searches

The LHC lifetime frontier will probe a dark sector in the near future, and the visible decay searches at fixed-target experiments have been exploring the dark sector. Dark strong dynamics provides rich structure in the dark sector: dark baryons and dark mesons. Dark photons are also introduced to alleviate cosmological problems. Meanwhile, dark photons make dark hadrons long-lived in terrestrial experiments. Moreover, the dark hadrons are produced through the very same dark photon. In this study, we discuss the visible decay searches for composite asymmetric dark matter and dark pion dark matter. The LHC lifetime frontier (MATHUSLA, FASER, and FACET) has a potential to discover the transition and decay of dark hadrons for a specific spectrum. For composite asymmetric dark matter models, the visible signals arise from dark nucleon transition and dark pion decay. These projected sensitivities to dark hadrons in dark photon parameter space are comparable with the future sensitivities of dark photon searches, such as Belle-II and LHCb. Meanwhile, for the dark pion dark matter model, the visible signals arise from dark vector-meson decay. Depending on the mass spectrum, these sensitivities are comparable with the dark photon searches such as DarkQuest, Belle-II, LHCb, and HPS.

Speaker: Takumi Kuwahara

LLP2024_Kuwahara.pdf

17:20 Future lepton beam dumps constraint on light bosons with lepton flavor violating couplings

We consider charged lepton flavor violation (CLFV) via a light and weakly interacting boson and discuss the detectability by future lepton beam dump experiments. We focus on three types of CLFV interactions, i.e., the scalar-, pseudoscalar-, and vector-type interactions, and calculate the sensitivities of lepton beam dumps to each CLFV interaction. We show that a wide region of the parameter space can be explored. Particularly, it is found that future lepton beam dump experiments have sensitivities to very small coupling regions in which the rare muon decays, such as $\mu \to e \gamma$, cannot place bounds, and that there is a possibility to detect CLFV decays of the new light bosons.

Speaker: Kento Asai (Institute for Cosmic Ray Research, The University of Tokyo)

LLP2024_KentoAsai.pdf

17:40 → 19:10 Breaks: Welcome reception

Tuesday 2 July

09:30 → 10:30 Theory and phenomenology

09:30 Heavy Neutrino-Antineutrino Oscillations at the FCC-ee

The observed small neutrino masses can be explained by type I seesaw models that predict the existence of heavy neutrinos. In a large part of the collider-accessible parameter space, these heavy neutral leptons would be long-lived and can be searched for with displaced vertex signatures. Additionally, collider-observable heavy neutrinos of type I seesaw models must form almost mass-degenerate pseudo-Dirac pairs as is for example captured by symmetry-protected seesaw models. Their tiny mass splitting induces heavy neutrino-antineutrino oscillations. We demonstrate the remarkable potential a Z-pole run of future lepton colliders such as the FCC-ee has to resolve these oscillations using angular distributions and displaced vertex signatures. Such a measurement would quantify the amount of lepton number violation present in the neutrino sector.

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 - Heavy Neutrino-Antineutrino Oscillations at the FCC-ee (LLP2024).pdf

09:50 Freeze-in sterile neutrino dark matter in feeble gauged $B-L$ model

We consider the gauged $U(1)_{B-L}$ model and examine the situation where the sterile neutrino becomes a dark matter candidate by the freeze-in mechanism. In our model, the dark matter $N$ is mainly produced by the decay of a $U(1)_{B-L}$ breaking scalar field $\phi$. We point out that the on-shell production of $\phi$ through annihilation of the $U(1)_{B-L}$ gauge field $Z’$ plays an important role. We find that the single production of $Z’$ from the photon bath is one of the main production processes of $Z’$. To prevent $N$ from being overproduced, we show that the $U(1)_{B-L}$ gauge coupling constant $g_{B-L}$ must be as small as $10^{-13}$--$10^{-10}$. We also consider the case where the decay of $\phi$ into $N$ is kinematically forbidden. In this case, $N$ is generated by the scattering of $Z'$ and the $g_{B-L}$ takes values of $10^{-7}$--$10^{-6}$, which can be explored in collider experiments like FASER.

Speaker: Takashi Shimomura

LLP2024-shimomura.pdf

10:10 Probing sterile neutrino magnetic moments with non-pointing photon searches at the LHC

In this talk, we explore long-lived particle (LLP) searches using non-pointing photons at the LHC as a probe for transition magnetic dipole moments of sterile neutrinos. We consider two heavy sterile neutrinos with masses ranging from a few GeV to several hundreds of GeV, which interact with the Standard Model (SM) through sterile-to-sterile and active-to-sterile dipole moments. In certain regions of the model parameter space, the sterile neutrinos have sizable decay lengths, leading to distinctive LLP signatures at colliders, such as displaced photons. Results of our numerical simulations reveal that non-pointing photon searches can be sensitive to sterile-to-sterile and active-to-sterile magnetic moments several orders of magnitude below existing limits.

Speaker: Rebeca Beltran (IFIC (CSIC-UV))

LLP2024_RebecaBeltran.pdf

10:30 → 11:00 Breaks: Coffee break

11:00 → 12:00 Dedicated or uniquely-sensitive long-lived particle detectors

11:00 DAMSA

Speaker: Un Ki Yang (Seoul National University (KR))

damsa-llp24.pdf

11:20 Forward Liquid Argon Experiment at the High Luminosity LHC

The Forward Liquid Argon Experiment (FLArE) is a Liquid Argon Time Projection Chamber (LArTPC) based experiment, designed to detect collider neutrinos and search for dark matter at the Large Hadron Collider (LHC) at CERN. It will be located in the proposed Forward Physics Facility (FPF), 620 m from the ATLAS interaction point in the far-forward direction. The LArTPC technology offers excellent spatial resolution and particle identification. With a fiducial mass of 10 tonnes, FLArE is able to detect millions of neutrinos from the LHC, and search for dark matter particles with world-leading sensitivity in the MeV to GeV mass range. In this talk, I will overview the physics reach, preliminary design, and status of the FLArE project.

Speaker: Wenjie Wu (University of California, Irvine)

20240702@LLP-FLArEStatus.pdf

11:40 EBES

Speaker: Taikan Suehara (ICEPP, The University of Tokyo (JP))

240702-llp2024-ebes-suehara.pdf

12:00 → 13:30 Breaks: Lunch

13:30 → 14:30 Dedicated or uniquely-sensitive long-lived particle detectors

13:30 The MoEDAL-MAPP New Physics Search Facility at the LHC

The MoEDAL experiment at IP8 on the LHC ring is the 7th LHC experiment and the first dedicated to the search for BSM physics. It took data at LHC’s Run-1&2. The MoEDAL detector is an unconventional and mostly passive detector dedicated to the search for Highly Ionizing Particle (HIP) avatars of new physics such as magnetic monopoles, Q-balls, dyon, microscopic black-hole remnants, and massive (peudo-)stable charged or multiply charged particles. An upgraded MoEDAL detector, installed for Run-3, with improved sensitivity is currently taking data. A new calibration of MoEDAL’s CR-39 Nuclear Track Detectors allows us to also search for massive singly & multiply electrically charged Long-Lived Particles (LLPs).

MoEDAL-MAPP is currently installing the MoEDAL Apparatus for Penetrating Particles (MAPP-1) in the UA83 tunnel ~100m from IP8 as part of MoEDAL-MAPP’s New Physics Search Facility at the LHC. MAPP-1 extends MoEDAL’s reach to include sensitivity to Feebly Ionizing Particles (FIPs) such as milli-charged particles and other weakly ionizing particle avatars of new physics. MAPP-1 also has sensitivity to charged and neutral LLPs. The MoEDAL-MAPP Collaboration plans to add the MAPP-2 detector to the Search Facility for data taking at the High Luminosity LHC to greatly enhance our sensitivity to neutral LLPs. We are proposing to deploy MAPP-2 in the UGC1 gallery adjacent to IP8. Both MAPP-1 and MAPP-2 are sensitive to charged and photonic decays from, for example, dark sector, heavy neutrino, mirror-world and supersymmetric scenarios.

Speaker: James Pinfold (University of Alberta (CA))

LLP2024-MoEDAl-MAPP -Talk.pdf

13:50 milliQan

Speaker: Sai Neha Santpur (Univ. of California Santa Barbara (US))

Google slides

MilliQan_Neha_LLP2024-2.pdf

14:10 LUXE

Speaker: Raquel Quishpe Quishpe (Karlsruhe Institute of Technology)

LUXE_NPOD_LLP24.pdf

14:30 → 15:00 Breaks: Coffee break

15:00 → 16:00 Dedicated or uniquely-sensitive long-lived particle detectors

15:00 The BDF/SHiP experiment at the ECN3 high-intensity beam facility at the CERN SPS

The BDF/SHiP experiment is a general purpose intensity-frontier experiment for the search of 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. The CERN Research Board recently decided in favour of BDF/SHiP for the future physics programme of this facility. BDF/SHiP will take full advantage of the available 4x10$^{19}$ protons per year at 400 GeV. The experimental setup consists of two complementary detectors downstream an active muon shield. The magnetic muon shield is placed directly after the target region and is designed to deflect the muons produced in the beam dump and thus reduce the flux in the detectors to an acceptable level. The first detector system, the scattering and neutrino detector (SND), consists of a light dark matter (LDM) / neutrino target with vertexing capability in the form of tungsten plates, alternated with emulsion films and fast electronic detector planes, followed by a muon spectrometer. The second detector system, the hidden sector decay spectrometer (HSDS), consists of a 50 m long decay volume followed by a large spectrometer, a timing detector and a PID system. This unique setup offers an unprecedented sensitivity to decay and scattering signatures of models with feebly interacting particles, such as dark-sector mediators and light dark matter, and allow high statistics studies of tau neutrino interactions.

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

LLP24_Magnan_Ship.pdf

15:20 Long-lived BSM signatures at ProtoDUNE

Speakers: Animesh Chatterjee (CERN), Laura Molina Bueno (Univ. of Valencia and CSIC (ES))

molina_LLP2024_2072024_v2.pdf

15:40 Exploring dark sectors at the NA64 experiment

The NA64 fixed-target experiment at CERN explores the existence of feebly interacting particles from dark sectors. Employing secondary high-energy electron, positron, muon and hadron beams from the Super Proton Synchrotron, NA64 seeks signs of dark particle production within an active beam dump, measuring missing energy and displaced vertex events. Through its high-intensity data collection, the experiment establishes forefront constraints in the light dark matter parameter space. This talk will detail the diverse search directions and present the latest results from the NA64 collaboration.

Speaker: Martina Mongillo (ETH Zurich (CH))

LLP2024_NA64_Mongillo.pdf

16:00 → 16:30 Breaks: Coffee break

16:30 → 17:20 Overviews: Capstone talk

16:30 Capstone talk: Quantum-limited ultra low threshold charge and energy detectors

Speaker: Daniel Carney (Berkeley National Lab)

2024 - tokyo LLP - carney.pdf

Wednesday 3 July

09:30 → 10:50 Experimental results from LHC

09:30 ATLAS: dE/dx + beta calo

Speaker: Alexis Elizabeth Mulski (Harvard University (US))

amulski_LLP_Workshop_2024_Final.pdf

09:50 CMS: Emerging jets

Speaker: Claire Savard (University of Colorado Boulder (US))

LLPW_EMJ_6_3_24.pdf

10:10 CMS: Trigger update (2023+2024)

Speaker: Kiley Elizabeth Kennedy (Princeton University (US))

LLP24_LLPTriggersCMS_KKennedy_07.03.2024

LLP24_LLPTriggersCMS_KKennedy_07.03.2024.pdf

10:30 CMS: LLPs in the muon detectors

Speaker: Christina Wenlu Wang (California Institute of Technology (US))

LLP14_Christina_Wang.pdf

10:50 → 11:20 Breaks: Coffee break

11:20 → 12:20 Theory and phenomenology

11:20 Mediator Decay through mixing with Degenerate Spectrum

Speaker: Ayuki Kamada

kamada0703.pdf

11:40 ANUBIS: Sensitivity studies with the SET-ANUBIS framework

New long-lived particles (LLPs) are a class of particles that are generically predicted in various theoretical extensions of the Standard Model (SM) such as those with Dark Matter candidates. The LHC has a detailed programme to search for LLPs produced at energies at the electroweak scale and above, which has mostly been focused on ‘prompt’ decays within the LHC experiments. In contrast, the ANUBIS experiment has been proposed to exploit the available space in the ATLAS cavern to search for LLPs with decay lengths of O(10m) and above. To do so the ceiling and bottom of the service shafts above the ATLAS experiment will be instrumented with tracking stations. This talk will present the latest results of ANUBIS’ sensitivity to a variety of new physics models that predict LLP signatures, focusing on Heavy Neutral Leptons, using the SET-ANUBIS framework. This newly developed framework aims to provide an easy way to simulate and compare a variety of models at ANUBIS.

Speaker: Paul Nathaniel Swallow (University of Cambridge (GB))

20240702__LL14_proANUBIS__Sensitivity_Studies_v2.pdf

12:00 SModelS v3: Beyond Z_2 Topologies

Speaker: Sabine Kraml (LPSC Grenoble)

skraml-llp-tokyo-24.pdf

12:20 → 14:00 Breaks: Lunch

14:00 → 22:00 Logistics: Excursions and dinner

Thursday 4 July

10:30 → 11:30 Experimental results from LHC

10:30 ATLAS: Higgs to displaced vertices

Speaker: Hamza Hanif (Simon Fraser University (CA))

hamza_llp_talk.pdf

10:50 ATLAS: Higgsino with displaced track

Speaker: Yuya Mino (Kyoto University (JP))

LLP2024_ymino.pdf

11:10 LHCb: searches for very long-lived particles

Speaker: Izaac Sanderswood (Univ. of Valencia and CSIC (ES))

llp2024_lhcb_very_long-lived_particles.pdf

11:30 → 12:00 Breaks: Coffee break

12:00 → 13:00 Experimental results from LHC

12:00 CMS: HNLs in the muon system

Speaker: Ka Hei Martin Kwok (Fermi National Accelerator Lab. (US))

Kwok_HNL_with_MDS.pdf

12:20 CMS: HNLs in the b-parking dataset

Speaker: Anne-Mazarine Lyon (ETH Zurich (CH))

24_07_04_LLP2024_BHNL_slides_AMLyon.pdf

12:40 CMS: HNLs in semi-leptonic final states

Speaker: Mohamed Darwish (Baylor University (US))

LLP_workshop.pdf

13:00 → 14:30 Breaks: Lunch

14:30 → 15:30 Experimental results from LHC

14:30 CMS: HSCP (dE/dx in tracker)

Speaker: Lawrence Lee Jr (University of Tennessee (US))

070424_LLee_CMS_HSCP.pdf

14:50 CMS: Displaced vertices with MET

Speaker: Ang Li (Austrian Academy of Sciences (AT))

DV_MET_LLP2024.pdf

15:10 ATLAS: Displaced lepton jets (dark photon jets)

Speaker: Richards González (The University of Edinburgh (GB))

dLJRun2n3_LLP2024_050724.pdf

15:30 → 16:00 Breaks: Coffee break

16:00 → 17:20 Experimental results from LHC

16:00 CMS: Displaced dijets in 2022 data

Speaker: Jingyu Luo (Brown University (US))

DisplacedJets_LLP14.pdf

16:20 A novel method to improve displaced dimuon searches

Speaker: Attilio Santocchia (Universita e INFN, Perugia (IT))

2024.07.04.LLP-Delphes.pdf

16:40 ATLAS: HIP/monopole

Speaker: Ana Maria Rodriguez Vera (Northern Illinois University (US))

HIP_AMRV.pdf

17:00 CMS: Displaced dimuons in 2022 data

Speaker: Mangesh Sonawane (Austrian Academy of Sciences (AT))

2024.07.04 _ LLP2024 - Displaced Dimuons Run 3 - v5.pdf

Friday 5 July

09:30 → 10:30 Forward LLPs at the LHC

09:30 FPF

Speakers: Felix Kling (DESY), Felix Kling (University of California, Irvine)

FPF@LLP2024.pdf

09:50 FASER BSM results

Speaker: Yuxiao Wang (Tsinghua University (CN))

LLP2024-yuxiao.pdf

10:10 New neutrino results from the FASER experiment at the LHC

The ForwArd Search ExpeRiment (FASER) is located at the LHC at CERN and studies long-lived, weakly interacting particles produced in the forward direction of the ATLAS interaction point. The FASER$\nu$ detector, the primary component for neutrino detection, is composed of a high-density structure with a total mass of 1.1 tons of tungsten plates interleaved with emulsion films to allow LLPs and neutrinos to interact inside the detector. It focuses on the measurement of three generations of neutrinos in the TeV energy region. This talk will present results from the current analysis, which detects several electron neutrino and muon neutrino events, and measures the cross sections. These are the first measurements in the unexplored TeV energy region.

Speaker: Motoya Nonaka (Chiba University (JP))

FASERnu_LLP_Nonaka.pdf

10:30 → 11:00 Breaks: Coffee break

11:00 → 12:00 Forward LLPs at the LHC

11:00 Dark photon pair production via off-shell dark higgs at FASER

FASER searches new long lived particles. We discuss the model in which we localize extra U(1) symmetry and it is broken by dark higgs taking vacuum expectation value. We calculated FASER’s sensitivity to dark photon from off-shell dark higgs decay numerically. We find that the sensitivity region can be spanned to unexplored region compared with other production process of dark photon. We also show the parameter space in which perturbative calculation is valid from unitarity of S matrix.

Speaker: Mr Youhei Nakashima (Kyushu University)

Nakashima_LLP2024.pdf

11:20 Recent results from the SND@LHC experiment

SND@LHC started taking data at the beginning of Run 3 of the LHC. The experiment is designed to perform measurements with neutrinos produced in proton-proton collisions at the LHC in an energy range between 100 GeV and 1 TeV. It covers a previously unexplored pseudo-rapidity range of 7.2 < η < 8.4. The detector is located 480 m downstream of the ATLAS interaction point in the TI18 tunnel. The detector is composed of a hybrid system based on an 800 kg target mass of tungsten plates, interleaved with emulsion and electronic trackers, followed downstream by a calorimeter and a muon system. The configuration allows efficiently distinguishing between all three neutrino flavours, opening a unique opportunity to probe physics of heavy flavour production at the LHC in the region that is not accessible to ATLAS, CMS and LHCb. This region is of particular interest also for future circular colliders and for predictions of very high-energy atmospheric neutrinos. The detector concept is also well suited to searching for Feebly Interacting Particles via signatures of scattering in the detector target. The experiment has published several results. This talk will focus on the experience gained from the first measurements and how this is being used to achieve the physics goals of SND@LHC.

Speaker: Masahiro Komatsu (Nagoya University (JP))

SNDLHC-LLP2024-Komatsu.pdf

11:40 FORMOSA

Speaker: Juan Salvador Tafoya Vargas (University of California Davis (US))

Formosa_JuanTafoya_LLP2024.pdf

12:00 → 13:30 Breaks: Lunch

13:30 → 14:50 Theory and phenomenology

13:30 Displaced ALPs from top decays at the LHC

I will present a study on axion-like particles (ALPs) with quark-flavor-violating couplings at the LHC. The ALPs can originate from decays of top quarks which are pair produced, and then decay to jets. If these couplings to the quarks are tiny and the ALPs have masses of the order of 10 GeV, they are long-lived, leading to signatures of displaced vertex plus multiple jets. We recast a recent ATLAS search for the same signature and reinterpret the results in terms of bounds on the long-lived ALP in our theoretical scenario. We find that the LHC with the full Run 2 dataset can place stringent limits, while at the future high-luminosity LHC stronger sensitivities are expected.

Speaker: Giovanna Cottin (Pontificia Universidad Católica de Chile (CL))

LLP24_TOKYO.pdf

13:50 Precise Estimate of Charged Higgsino/Wino Decay Rate

Speaker: Satoshi Shirai (Kavli IPMU)

Shirai.pdf

14:10 Long-lived particle searches with the ILD experiment

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

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

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

Speaker: Jan Franciszek Klamka (University of Warsaw (PL))

jklamka_llp2024.pdf

14:30 New constraints on LLPs by T2K near detector

We study the capability of the off-axis near detector ND280 of the T2K experiment to search for LLPs, and show constraints on the dark photon model and the B-L model. It is found that the ten-year operation of T2K with the ND280 detector excludes the unexplored parameter region of the models. We also show that a broader parameter region can be searched by the ND280 in the future T2K operation.

Speaker: Takeshi Araki (Ohu University)

ARAKI_DP@T2K-ND280.pdf

14:50 → 15:20 Breaks: Coffee break

15:20 → 16:20 Long-lived particles from unique hadron sources

15:20 SHiNESS: Search for Hidden Neutrinos at the ESS

Speakers: Stefano Roberto Soleti, Stefano Roberto Soleti, Stefano Roberto Soleti (Lawrence Berkeley National Laboratory), Stefano Roberto Soleti (Donostia International Physics Center)

shiness_llp.pdf

15:40 Light new physics in proton decays

The difference between baryon- and lepton number, $B-L$, is a conserved charge in the Standard model. However, its violation is needed in order to explain the dynamical origin of the matter-antimatter asymmetry, and possibly also neutrino masses. One way to search for $B-L$ violation is via proton decays, such as in the upcoming experiments at DUNE, JUNO, and Hyper-K. However, only proton decay modes with Standard model particles in the final state have been searched for so far. Long-lived new particles such as axions, scalar dark matter, sterile neutrinos, dark photons, etc, may also be involved in proton decays if their mass is sufficiently low. We provide a set of effective operators that could lead to such non-standard decay modes, and show how the resulting kinematics can be distinguished from the corresponding Standard model final states. Finally, we show how these modes could arise in SO(10) as well as a leptoquark model example.

Speaker: Kåre Fridell (KEK, Tsukuba)

LLP 2024 Proton decay.pdf

16:00 The new physics potential of free neutron-antineutron oscillations at the ESS

If a beam of slow neutrons ($n$) (with kinetic energies less than a few meV) is produced and allowed to propagate through a magnetically shielded vacuum (~nT) before letting it hit a target, then in the presence of baryon number violating interactions some $n$'s can oscillate into $\bar{n}$'s. The produced $\bar{n}$'s can annihilate with the target material producing detectable final state particles e.g. photons and pions. The ESS/NNBAR facility (expected to employ an impressive 200m long propagation length) is expected to improve the sensitivity to the free $n-\bar{n}$ oscillations by three orders of magnitude over the last such search at the ILL. This talk will discuss the exciting physics prospects and phenomenological implications of searches for $n-\bar{n}$ oscillations.

Speaker: Chandan Hati (Valencia U., IFIC)

LLP_CH_2024.pdf

16:20 → 16:30 Logistics: Farewell

16:20 Looking forward to LLP2025 in Valencia

Speaker: Dr José Francisco Zurita (IFIC - Univ. of Valencia and CSIC (ES))

Looking_forward_to_LLP2025.pdf