LLP2024: Fourteenth workshop of the Long-Lived Particle Community
University of Tokyo
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.
Aashaq Shah
Andre Frankenthal
Andre Lessa
Andrii Usachov
Anne-Marie Magnan
Atsuya Niki
Audrey Kvam
Chandan Hati
Daniel Carney
Dipan Sengupta
Erez Etzion
Hoyong Jeong
Jan Franciszek Klamka
José Francisco Zurita
Justin Kerr
K.K. Gan
Ka Hei Martin Kwok
Kiley Kennedy
Mangesh Sonawane
Masahiro Komatsu
Osamu Jinnouchi
Sai Neha Santpur
Stefano Giagu
Takeshi Araki
Tova Ray Holmes
Yuxiao Wang
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Logistics: Registration
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Logistics: Introduction
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09:30
Welcome from the University of Tokyo 10mSpeaker: Toshinori Mori (University of Tokyo (JP))
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09:40
Introduction to the Long-Lived Particle Community 10mSpeaker: James Beacham (Duke University (US))
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09:50
Logistics and contents of the LLP2024 edition 10mSpeakers: Carlos Vazquez Sierra (Universidade de Santiago de Compostela (ES)), Ryu Sawada (University of Tokyo (JP))
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Overviews: CMS, ATLAS and LHCb Koshiba Main Hall
Koshiba Main Hall
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Overview of CMS results 30mSpeaker: Andre Frankenthal (Princeton University (US))
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Breaks: Coffee break
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Overviews: Belle-II and BES-III Koshiba Main Hall
Koshiba Main Hall
- 11:50
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12:20
Searches for dark sector particles at Belle and Belle II 30m
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)
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Logistics: Workshop picture
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Breaks: Lunch
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Dedicated or uniquely-sensitive long-lived particle detectors Koshiba Main Hall
Koshiba Main Hall
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14:30
COmpact DEtector for EXotics at LHCb: CODEX-b 20m
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)) - 14:50
- 15:10
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ANUBIS: Initial commissioning results from proANUBIS 20m
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))
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Breaks: Coffee break
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Theory and phenomenology Koshiba Main Hall
Koshiba Main Hall
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Simplified t-channel dark matter models and long-lived particles 20m
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) -
16:40
Dark Showers with the Z-portal 20m
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 -
17:00
Confining Dark Sector and Long-lived Particle Searches 20m
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 -
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Future lepton beam dumps constraint on light bosons with lepton flavor violating couplings 20m
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)
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Breaks: Welcome reception
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Theory and phenomenology Koshiba Main Hall
Koshiba Main Hall
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Heavy Neutrino-Antineutrino Oscillations at the FCC-ee 20m
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)) -
09:50
Freeze-in sterile neutrino dark matter in feeble gauged $B-L$ model 20m
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 -
10:10
Probing sterile neutrino magnetic moments with non-pointing photon searches at the LHC 20m
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))
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Breaks: Coffee break
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Dedicated or uniquely-sensitive long-lived particle detectors Koshiba Main Hall
Koshiba Main Hall
- 11:00
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Forward Liquid Argon Experiment at the High Luminosity LHC 20m
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) -
11:40
EBES 20mSpeaker: Taikan Suehara (ICEPP, The University of Tokyo (JP))
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Breaks: Lunch
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Dedicated or uniquely-sensitive long-lived particle detectors Koshiba Main Hall
Koshiba Main Hall
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The MoEDAL-MAPP New Physics Search Facility at the LHC 20m
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)) -
13:50
milliQan 20mSpeaker: Sai Neha Santpur (Univ. of California Santa Barbara (US))
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Breaks: Coffee break
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Dedicated or uniquely-sensitive long-lived particle detectors Koshiba Main Hall
Koshiba Main Hall
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15:00
The BDF/SHiP experiment at the ECN3 high-intensity beam facility at the CERN SPS 20m
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)) -
15:20
Long-lived BSM signatures at ProtoDUNE 20mSpeakers: Animesh Chatterjee (CERN), Laura Molina Bueno (Univ. of Valencia and CSIC (ES))
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Exploring dark sectors at the NA64 experiment 20m
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))
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Breaks: Coffee break
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Overviews: Capstone talk Koshiba Main Hall
Koshiba Main Hall
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Capstone talk: Quantum-limited ultra low threshold charge and energy detectors 50mSpeaker: Daniel Carney (Berkeley National Lab)
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Experimental results from LHC Koshiba Main Hall
Koshiba Main Hall
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ATLAS: dE/dx + beta calo 20mSpeaker: Alexis Elizabeth Mulski (Harvard University (US))
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09:50
CMS: Emerging jets 20mSpeaker: Claire Savard (University of Colorado Boulder (US))
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10:10
CMS: Trigger update (2023+2024) 20mSpeaker: Kiley Elizabeth Kennedy (Princeton University (US))
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10:30
CMS: LLPs in the muon detectors 20mSpeaker: Christina Wenlu Wang (California Institute of Technology (US))
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Breaks: Coffee break
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Theory and phenomenology Koshiba Main Hall
Koshiba Main Hall
- 11:20
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11:40
ANUBIS: Sensitivity studies with the SET-ANUBIS framework 20m
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)) - 12:00
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Breaks: Lunch
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Logistics: Excursions and dinner
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Experimental results from LHC Koshiba Main Hall
Koshiba Main Hall
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ATLAS: Higgs to displaced vertices 20mSpeaker: Hamza Hanif (Simon Fraser University (CA))
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10:50
ATLAS: Higgsino with displaced track 20mSpeaker: Yuya Mino (Kyoto University (JP))
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11:10
LHCb: searches for very long-lived particles 20mSpeaker: Izaac Sanderswood (Univ. of Valencia and CSIC (ES))
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Breaks: Coffee break
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Experimental results from LHC Koshiba Main Hall
Koshiba Main Hall
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12:00
CMS: HNLs in the muon system 20mSpeaker: Ka Hei Martin Kwok (Fermi National Accelerator Lab. (US))
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12:20
CMS: HNLs in the b-parking dataset 20mSpeaker: Anne-Mazarine Lyon (ETH Zurich (CH))
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12:40
CMS: HNLs in semi-leptonic final states 20mSpeaker: Mohamed Darwish (Baylor University (US))
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Breaks: Lunch
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Experimental results from LHC Koshiba Main Hall
Koshiba Main Hall
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CMS: HSCP (dE/dx in tracker) 20mSpeaker: Lawrence Lee Jr (University of Tennessee (US))
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14:50
CMS: Displaced vertices with MET 20mSpeaker: Ang Li (Austrian Academy of Sciences (AT))
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15:10
ATLAS: Displaced lepton jets (dark photon jets) 20mSpeaker: Richards González (The University of Edinburgh (GB))
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Breaks: Coffee break
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Experimental results from LHC Koshiba Main Hall
Koshiba Main Hall
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16:00
CMS: Displaced dijets in 2022 data 20mSpeaker: Jingyu Luo (Brown University (US))
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16:20
A novel method to improve displaced dimuon searches 20mSpeaker: Attilio Santocchia (Universita e INFN, Perugia (IT))
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16:40
ATLAS: HIP/monopole 20mSpeaker: Ana Maria Rodriguez Vera (Northern Illinois University (US))
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17:00
CMS: Displaced dimuons in 2022 data 20mSpeaker: Mangesh Sonawane (Austrian Academy of Sciences (AT))
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Forward LLPs at the LHC
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FPF 20mSpeakers: Felix Kling (DESY), Felix Kling (University of California, Irvine)
- 09:50
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New neutrino results from the FASER experiment at the LHC 20m
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))
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Breaks: Coffee break
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Forward LLPs at the LHC
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11:00
Dark photon pair production via off-shell dark higgs at FASER 20m
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) -
11:20
Recent results from the SND@LHC experiment 20m
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)) -
11:40
FORMOSA 20mSpeaker: Juan Salvador Tafoya Vargas (University of California Davis (US))
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Breaks: Lunch
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Theory and phenomenology Koshiba Main Hall
Koshiba Main Hall
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Displaced ALPs from top decays at the LHC 20m
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)) -
13:50
Precise Estimate of Charged Higgsino/Wino Decay Rate 20mSpeaker: Satoshi Shirai (Kavli IPMU)
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Long-lived particle searches with the ILD experiment 20m
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)) -
14:30
New constraints on LLPs by T2K near detector 20m
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)
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Breaks: Coffee break
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Long-lived particles from unique hadron sources
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SHiNESS: Search for Hidden Neutrinos at the ESS 20mSpeakers: Stefano Roberto Soleti, Stefano Roberto Soleti, Stefano Roberto Soleti (Lawrence Berkeley National Laboratory), Stefano Roberto Soleti (Donostia International Physics Center)
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15:40
Light new physics in proton decays 20m
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) -
16:00
The new physics potential of free neutron-antineutron oscillations at the ESS 20m
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)
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15:20
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16:20
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Logistics: Farewell
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16:20
Looking forward to LLP2025 in Valencia 10mSpeaker: Dr José Francisco Zurita (IFIC - Univ. of Valencia and CSIC (ES))
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16:20
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