Searching for long-lived particles at the LHC and beyond: Tenth workshop of the LLP Community

9 Nov 2021, 07:40 → 12 Nov 2021, 21:00 Europe/Zurich

Virtually, worldwide

James Beacham (Duke University (US)), Lisa Benato (Hamburg University (DE)), Margaret Susan Lutz (Tel Aviv University (IL)), Carlos Vazquez Sierra (CERN), Federico Leo Redi (CERN), José Francisco Zurita (IFIC - Univ. of Valencia and CSIC (ES)), Karri Folan Di Petrillo (Fermi National Accelerator Lab. (US)), Louie Dartmoor Corpe (CERN), Matthew Daniel Citron (Univ. of California Santa Barbara (US)), Sascha Mehlhase (LMU Munich), Albert De Roeck (CERN)

https://cern.ch/longlivedparticles

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The tenth LLP Community workshop will occur from 9 to 12 November, 2021, fully virtually again, and the agenda is now live!

Please join us for the hottest-and-latest in LLPs around the globe.

Tuesday 9 November

1 Welcome and introduction

Speaker: James Beacham (Duke University (US))

Beacham_LLPX_Tenth_LLP_Community_Intro_2021Nov9.pdf

Dedicated LLP detectors and projects: Session 1

Conveners: Albert De Roeck (CERN), Karri Folan Di Petrillo (Fermi National Accelerator Lab. (US))

2 Why so many LLP detectors?

Speaker: Matthew Daniel Citron (Univ. of California Santa Barbara (US))

whySoManyDetectors_LLPX_MC.pdf

3 SHADOWS (20+5)

We propose a new beam-dump experiment, SHADOWS, to search for a large variety of feebly-interacting particles possibly produced in the interactions of a 400 GeV proton beam with a high-Z material dump. SHADOWS will use the 400 GeV primary proton beam extracted from the CERN SPS currently serving the NA62 experiment in the CERN North area and will take data off-axis when the P42 beam line is operated in beam-dump mode. SHADOWS can accumulate up to a ~2 x10^19 protons on target per year and expand the exploration for a large variety of FIPs well beyond the state-of-the-art in the mass range of MeV-GeV in a parameter space that is allowed by cosmological and astrophysical observations. So far the strongest bounds on the interaction strength of new feebly-interacting light particles with Standard Model particles exist up to the kaon mass; above this threshold the bounds weaken significantly. SHADOWS can do an important step into this still poorly explored territory and has the potential to discover them if they have a mass between the kaon and the beauty mass. If no signal is found, SHADOWS will push the limits on their couplings with SM particles between one and four orders of magnitude in the same mass range, depending on the model and scenario.

Speaker: Gaia Lanfranchi (INFN e Laboratori Nazionali di Frascati (IT))

LLPX_Lanfranchi.pdf

4 SUBMET (12+5)

We studied the feasibility of an experiment searching for sub-millicharged particles (χs) using 30 GeV proton fixed-target collisions at J-PARC. The detector is composed of two layers of stacked scintillator bars and PMTs and is proposed to be installed 280 m from the target. The main background is a random coincidence between two layers due to dark counts in PMTs, which can be reduced to a negligible level using the timing of the proton beam. With NPOT=1022 which corresponds to running the experiment for three years, the experiment provides sensitivity to χs with the charge down to 5×10−5 in mχ<0.2 GeV/c2 and 8×10−4 in mχ<1.6 GeV/c2. This is the regime largely uncovered by the previous experiments. We also explored a few detector designs to achieve an optimal sensitivity to χs. The photoelectron yield is the main driver, but the sensitivity does not have a strong dependence on the detector configuration in the sub-millicharge regime.

Speaker: Jae Hyeok Yoo (Korea University (KR))

20211109_submet_llpx.pdf

5 MoEDAL (12+5)

We shall present the latest results from the MoEDAL-MAPP experiment and a review of ongoing and future work on the search for HIPs. In addition, we shall review the status of the MAPP Phase-1 extension to the MoEDAL experiment to be deployed in UA83. the MAPP Phase-1 and Phase-2 detectors are designed to extend the physics reach of MoEDAL to include mCP effectively mCP, LLP and LLCP avatars of new physics.

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

Presentation-LLP-10.pdf

15:19 Coffee

Dedicated LLP detectors and projects: Session 2

Conveners: Federico Leo Redi (CERN), Dr Louie Dartmoor Corpe (CERN)

6 Long-lived particles at the LUXE experiment (12+5)

The proposed LUXE experiment (LASER Und XFEL Experiment) at DESY, Hamburg, using the electron beam from the European XFEL, aims to probe QED in the non-perturbative regime created in collisions between high-intensity laser pulses and high-energy electron or photon beams. This setup also provides a unique opportunity to probe physics beyond the standard model. In this talk we show that by leveraging the large photon flux generated at LUXE, one can probe long-lived axion-like-particles (ALPs) up to a mass of 350 MeV and with photon coupling of 3x10^{-6} GeV^{-1} as well as other long-lived scalars. This reach is comparable to FASER2 and NA62. In addition, we will discuss other probes of new physics such as ALPs-electron coupling.

Speaker: Federico Meloni (Deutsches Elektronen-Synchrotron (DE))

LUXE_BSM_LLPX.pdf

7 The SND@LHC experiment at CERN (12+5)

SND@LHC is a compact and stand-alone experiment to perform measurements with neutrinos produced at the LHC in a hitherto unexplored pseudo-rapidity region of 7.2 < 𝜂 < 8.6, complementary to all the other experiments at the LHC. The experiment is to be located 480 m downstream of IP1 in the unused 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 first phase aims at operating the detector throughout LHC Run 3 to collect a total of 150 fb−1. We report here the status of detector construction and its physics case.

Speaker: Eric Van Herwijnen (National University of Science and Technology "MISIS" (RU))

LLP_09112021.pdf

LLP_09112021.pptx

8 Status of the Run 3 milliQan detector (12+5)

In the previous LLP workshop we presented our design for the next generation milliQan detectors and their expected combined sensitivity with the Run 3 dataset. For this meeting, we will present the progress on the construction of these detectors, which are planned to be installed in PX56 at LHC P5, above CMS, prior to the start of Run 3.

Speaker: Michael William Carrigan (Ohio State University (US))

MilliQanLLP.pptx

16:20 Coffee

Dedicated LLP detectors and projects: Session 3

Conveners: Albert De Roeck (CERN), Karri Folan Di Petrillo (Fermi National Accelerator Lab. (US))

9 FPF (20+5)

The Forward Physics Facility (FPF) is a proposal to create a cavern with the space and infrastructure to support a suite of far-forward experiments at the Large Hadron Collider during the High Luminosity era. Located along the beam collision axis and shielded from the interaction point by at least 100 m of concrete and rock, the FPF will house experiments that will detect particles outside the acceptance of the existing large LHC experiments and will observe rare and exotic processes in an extremely low-background environment. In this work, we summarize the current status of plans for the FPF, including recent progress in civil engineering in identifying promising sites for the FPF and the experiments currently envisioned to realize the FPF's physics potential. We then review the many Standard Model and new physics topics that will be advanced by the FPF, including searches for long-lived particles, probes of dark matter and dark sectors, high-statistics studies of TeV neutrinos of all three flavors, aspects of perturbative and non-perturbative QCD, and high-energy astroparticle physics.

Speaker: Jamie Boyd (CERN)

FPF-LLPworkshop-9.11.21.pdf

10 Detecting long-lived particles trapped in detector material at the LHC (12+5)

We propose to implement a two-stage detection strategy for exotic long-lived particles that could be produced at the CERN LHC, become trapped in detector material, and decay later. The proposed strategy relies on an array of metal rods, combined to form a high-density target. In a first stage, the rods are exposed to radiation from LHC collisions in one of the experimental caverns. In a second stage, they are individually immersed in liquid argon in a different experimental hall, where out-of-time decays could produce a detectable signal. Using a benchmark case of long-lived gluino pair production, we show that this experiment would be sensitive to a wide range of masses. Such an experiment would have unique sensitivity to gluino-neutralino mass splittings down to 3 GeV, in previously uncovered particle lifetimes ranging from days to years.

Speaker: Jan Kieseler (CERN)

TrapAndDetect_LLPX_Nov2021.pdf

11 CODEX-b (12+5)

CODEX-b is a promising proposal to detect LLPs at the LHC. CODEX-b will be situated next to the LHCb detector, behind a 3 m thick concrete radiation shield, approximately 25 m from the LHCb pp interaction point. In this talk we will present the status of CODEX-b as well as that of CODEX-beta, a demonstrator detector to be installed in the same location during Run 3 of the LHC.

Speaker: Louis Henry (CERN)

20211109_LLPX_CodexB.pdf

12 Progress on FASER and FASERnu (12+5)

The FASER experiment consists of two detectors, FASER and FASERnu, that will search for new particles and detect roughly 10,000 neutrino interactions at TeV energies in LHC Run 3. In this talk, we will present updates on the status of these detectors, including their construction, commissioning, results from test beam runs, and future prospects.

Speaker: Tobias Boeckh (University of Bonn (DE))

Status-of-the-FASER-Experiment.pdf

17:46 Workshop photo

17:51 Coffee

Dedicated LLP detectors and projects: Session 4

Conveners: James Beacham (Duke University (US)), Margaret Susan Lutz (Tel Aviv University (IL))

13 MATHUSLA (12+5)

The observation of long-lived particles at the LHC would reveal physics beyond the Standard Model, could account for the many open issues in our understanding of our universe, and conceivably point to a more complete theory of the fundamental interactions. Such long-lived particle signatures are fundamentally motivated and can appear in virtually every theoretical construct that address the Hierarchy Problem, Dark Matter, Neutrino Masses and the Baryon Asymmetry of the Universe. We describe in this document a large detector, MATHUSLA, located on the surface above an HL-LHC pp interaction point, that could observe long-lived particles with lifetimes up to the Big Bang Nucleosynthesis limit of 0.1 s. We also note that its large detector area allows MATHUSLA to make important contributions to cosmic ray physics. Because of the potential for making a major breakthrough in our conceptual understanding of the universe, long-lived particle searches should have the highest level of priority.

Speaker: Emma Torro Pastor (Univ. of Valencia and CSIC (ES))

Mathusla_LHCLLP_Nov2021.pdf

14 FACET (15+5)

We intend to develop a proposal to search for BSM long-lived particles (LLPs), such as dark photons with mA′ < 20 GeV, in the forward direction of IR5 (CMS), penetrating 35 m– 50 m of steel in the Q1 – Q3 quadrupoles and D1 dipole, and either decaying in a large vacuum pipe or interacting in an imaging calorimeter. Neutral LLPs with |η|> 8 decaying after traversing 83 m of vacuum may also be detected if their mass is several GeV.

Speaker: Dan Green (Fermi National Accelerator Lab. (US))

Status of FACET_11_2021_v4.ppt

18:37 Coffee

Status of LLPs searches at ATLAS, CMS, and LHCb: Snapshots

Conveners: Margaret Susan Lutz (Tel Aviv University (IL)), Matthew Daniel Citron (Univ. of California Santa Barbara (US))

15 LHCb snapshot

Speaker: Davide Zuliani (Universita e INFN, Padova (IT))

LLP2021_LHCb_zuliani.pdf

16 ATLAS snapshot

Speaker: Julia Lynne Gonski (Columbia University (US))

1109_jgonski_atlasLLPResultsSummary.pdf

17 CMS snapshot

Speaker: Mario Masciovecchio (Univ. of California San Diego (US))

Mario-Masciovecchio_LLPX_CMS.pdf

Wednesday 10 November

Belle II: (All talks 12+3)

Conveners: José Francisco Zurita (IFIC - Univ. of Valencia and CSIC (ES)), Dr Louie Dartmoor Corpe (CERN)

Recording

18 Probing charged lepton flavor violation with axion-like particles at Belle II

We study charged lepton flavor violation associated with a light leptophilic axion-like particle (ALP), $X$, at the $B$-factory experiment Belle II. We focus on production of the ALP in the tau decays $\tau \to X l$ with $l=e,\mu$, followed by its decay via $X\to l^- l^+$. The ALP can be either promptly decaying or long-lived. We perform Monte-Carlo simulations, recasting a prompt search at Belle for lepton-flavor-violating $\tau$ decays, and propose a displaced-vertex (DV) search. For both types of searches, we derive the Belle II sensitivity reaches in both the product of branching fractions and the ALP coupling constants, as functions of the ALP mass and lifetime. The results show that the DV search exceeds the sensitivity reach of the prompt search to the relevant branching fractions by up to about a factor of 40 in the long decay length regime.

Speaker: Zeren Simon Wang (National Tsing Hua University)

alp_belleII.pdf

19 Long-lived Sterile Neutrinos at Belle II in Effective Field Theory

At Belle II, large and clean samples of $\tau$ leptons are produced and may decay to sterile neutrinos. For the relevant mass range, such sterile neutrinos are typically long-lived, leading to displaced-vertex (DV) signatures at colliders. Here, we study a DV search of sterile neutrinos at Belle II in the framework of the sterile-neutrino-extended Standard Model Effective Field Theory ($\nu$SMEFT). The production and decay of the sterile neutrinos can be realized via either the standard active-sterile neutrino mixing or higher-dimensional operators in $\nu$SMEFT. We perform Monte-Carlo simulations to estimate the Belle II sensitivities to such sterile neutrinos, and find that Belle II can probe non-renormalizable dimension-six operators involving one sterile neutrino up to 3 TeV in the new-physics scale.

Speaker: Julian Günther

Sterile_Neutrinos_Belle_II_JG.pdf

20 Heavy QCD Axion at Belle II: Displaced and Prompt Signals

The QCD axion is a well-motivated addition to the standard model to solve the strong $CP$ problem. If the axion acquires mass dominantly from a hidden sector, it can be as heavy as $O(1)$ GeV, and the decay constant can be as low as $O(100)$ GeV without running into the axion quality problem. We propose new search strategies for such heavy QCD axions at the Belle II experiment, where the axions are expected to be produced via $B\to K a$. We find that a subsequent decay $a\to 3\pi$ with a displaced vertex leads to a unique signal with essentially no background, and that a dedicated search can explore the range $O(1$-$10)$ TeV of decay-constant values. We also show that $a\to \gamma\gamma$ can cover a significant portion of currently unexplored region of $150 < m_a < 500$ MeV.

Speaker: Vazha Loladze (Florida State University)

LLPX.pdf

21 Displaced or Invisible? ALPs from B decays at Belle II

At collider experiments, long-lived particles may decay displaced within the detector or leave the detector as missing energy, depending on their lifetime and on the detector geometry. To exploit this complementarity, we propose a new search strategy for invisible ALPs in $B^+\to K^+ a$ decays at Belle II. We compare our predictions with existing and future searches for displaced vertices from $B^+\to K^+ a(\to\mu^+\mu^-)$ decays. This example demonstrates how to maximize the sensitivity to long-lived particles over a wide range of lifetimes by combining searches with displaced vertices and missing energy.

Speaker: Ruth Schäfer

LLPX_RuthSchaefer_InvVsDisp.pdf

15:00 Coffee

Heavy neutral leptons (HNLs) session

Conveners: Albert De Roeck (CERN), Federico Leo Redi (CERN)

Recording

22 Introduction and news

Speaker: Federico Leo Redi (CERN)

HNL_LHC_introduction.pdf

23 Updates from theory, a personal perspective

Speaker: Marco Drewes (Universite Catholique de Louvain (UCL) (BE))

Drewes_LLPX_5.pdf

24 HNLs production from mesons

Speaker: Philip Ilten (University of Cincinnati (US))

ilten.pdf

Pythia for HNLs

16:10 Coffee

Status of LLPs searches at ATLAS, CMS, and LHCb: Recent results in detail

Conveners: Lisa Benato (Hamburg University (DE)), Margaret Susan Lutz (Tel Aviv University (IL))

Recording

25 ATLAS displaced vertices in the Muon Spectrometer

Speaker: Audrey Katherine Kvam (University of Washington (US))

Kvam_2vx_10Nov.pdf

26 CMS Displaced Leptons

Speaker: Bryan Cardwell (University of Virginia (US))

cardwell_displacedLeptons_llpx_10_11_2021.pdf

27 LHCb massive long-lived particles decaying semileptonically

Speaker: Davide Zuliani (Universita e INFN, Padova (IT))

LLP2021_massiveLLP_zuliani.pdf

28 CMS all hadronic stau search - with displaced tau regions

Speaker: Maria Giulia Collura (Univ. of California Santa Barbara (US))

211109_LLP.pdf

29 CMS Long-lived heavy neutral leptons (leptonic final state)

Speaker: Joscha Knolle (Ghent University (BE))

JK_211110_hnl_cms.pdf

18:00 Coffee

Quirks

Conveners: James Beacham (Duke University (US)), Karri Folan Di Petrillo (Fermi National Accelerator Lab. (US))

Recording

30 The quirk signal at the FASER (12+3)

We study the FASER sensitivity to the quirk signal by simulating the motions of quirks that are travelling through several infrastructures from the ATLAS interaction point to the FASER detector. The ionization energy losses for a charged quirk travelling in different materials are treated carefully. Assuming negligible background, the exclusion limits for quirks of four different quantum numbers are obtained for an integrated luminosity of 300 fb$^{-1}$. The features of the quirk signals at the FASER detector are also discussed.

Speaker: Mr Junle Pei (Institute of Theoretical Physics, Chinese Academy of Sciences)

Junle Pei.pdf

31 Why aren't there any quirks results from ATLAS or CMS yet? (12+3)

Speaker: Zach Marshall (Lawrence Berkeley National Lab. (US))

Marshall Quirks 2021.11.10.pdf

18:40 Coffee

Keynote talk: Theory and Simulation Challenges for Hidden Valleys/Dark Sectors

Conveners: James Beacham (Duke University (US)), Matthew Daniel Citron (Univ. of California Santa Barbara (US))

32 Theory and Simulation Challenges for Hidden Valleys/Dark Sectors

Speaker: Matt Strassler

LLP-X-Plenary-HVSimChallenges3.pdf

Recording

Thursday 11 November

Machine Learning for LLPs

Conveners: Federico Leo Redi (CERN), Lisa Benato (Hamburg University (DE))

Recording

33 Machine learning for LLP searches at the LHC and beyond: Overview and future (25+5)

Speaker: Gregor Kasieczka (Hamburg University (DE))

DeepLearning_LLP_2021.pdf

34 ABCD methods for LLP searches using ML (15+5)

Speaker: Gordon Watts (University of Washington (US))

2021-11-11 - The ABCD Method.pdf

2021-11-11 - The ABCD Method.pptx

35 Unsupervised SUEP (12+3)

Speaker: Aris-George-Baldur Spourdalakis

LLPX_presentation.pdf

36 ML for LLP searches: Discussion

Coffee

Re-interpretations and likelihoods: Part 1 (All talks 12+3)

Conveners: Karri Folan Di Petrillo (Fermi National Accelerator Lab. (US)), Lisa Benato (Hamburg University (DE))

Recording

37 Recasting long-lived particle searches at the LHC with CheckMATE 2

Speaker: Zeren Simon Wang (National Tsing Hua University)

CM2.pdf

GitHub - CheckMATE2-LLP

38 Recasting the CMS disappearing track search(es)

Speaker: Mark Dayvon Goodsell (Centre National de la Recherche Scientifique (FR))

HackAnalysis page

LLP recasting repo

LLPX.pdf

39 Dedicated Delphes Module for Neutral Long-lived Particles Decaying in the CMS Endcap Muon Detectors

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

CWang_LLPX_20211111.pdf

Coffee

Re-interpretations and likelihoods: Part 2

Conveners: Albert De Roeck (CERN), Matthew Daniel Citron (Univ. of California Santa Barbara (US))

40 Reinterpretation of novel CMS analysis in low-mass LLP models

Speaker: Andrea Mitridate

LLP@LHC.pdf

41 Exploring Uncharted Soft Displaced Vertices in Open Data

Speaker: Daneng Yang (Department of Physics, Tsinghua University (CN))

42 Recasting LHC searches for long-lived particles with MadAnalysis 5

Speaker: Jack Araz (IPPP - Durham University)

Ma5 - Home page

Ma5 - Launchpad

Public Analysis Database

Recasting LHC searches for long-lived particles with MadAnalysis 5

Re-interpretations and likelihoods: Joint session with RiF on publishing likelihoods

Conveners: Albert De Roeck (CERN), Louie Dartmoor Corpe (CERN)

Recording

43 Experience with LLP likelihoods from SModelS

Speaker: Sabine Kraml (LPSC Grenoble)

smodels-LLP.pdf

44 pyhf: intro from the developers

Speaker: Lukas Alexander Heinrich (CERN)

pyhfintro.pdf

45 Discussion on publishing likelihoods for LLP searches

Speaker: Dr Louie Dartmoor Corpe (CERN)

Coffee

Lightning round / new ideas: Session 1 (All talks 12+3)

Conveners: Dr Louie Dartmoor Corpe (CERN), Margaret Susan Lutz (Tel Aviv University (IL))

Recording

46 Tumblers: A Novel Collider Signature for Long-Lived Particles

Speaker: Doojin Kim (Texas A & M University (US))

Presentation_LLPX.pdf

47 Strangelets detection with large LAr detectors

Speaker: Mihaela Parvu (University of Bucharest (RO))

MParvu_Strangelets detection with LAr detectors_LLPX.pdf

48 Searching for light long-lived neutralinos at Super-Kamiokande

Speaker: Pablo Candia da Silva

Searching for light long-lived neutralinos at Super-Kamiokande.pdf

Friday 12 November

Lightning round / new ideas: Session 2

Conveners: Federico Leo Redi (CERN), José Francisco Zurita (IFIC - Univ. of Valencia and CSIC (ES))

Recording

49 Time-delayed electrons from neutral currents at the LHC

Speaker: Zeren Simon Wang (National Tsing Hua University)

nc_timing.pdf

50 Exploring long-lived particles and its properties at colliders

Speaker: Dong Woo Kang (KIAS)

LLPX_DWK.pdf

51 Heavy long-lived coannihilation partner from inelastic Dark Matter model and its signatures at the LHC [CANCELLED]

Speaker: Xiao-Ping Wang

52 Early Matter Domination from Long-Lived Particles in the Visible Sector

Speaker: Jacek Osinski (AstroCeNT, Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences)

EMD_LLP_Osinski.pdf

Coffee

Lightning round / new ideas: Session 3

Recording

53 Portal Effective Theories

Speaker: Jan Hajer (Universität Basel)

Portal effective theories

54 Long-lived HNLs in NRSMEFT

Speaker: Giovanna Cottin (Universidad Adolfo Ibañez)

LLPX_NRSMEFT_GCOTTIN.pdf

Coffee

Lightning round / new ideas: Session 4

Conveners: James Beacham (Duke University (US)), Louie Dartmoor Corpe (CERN)

Recording

55 Simulating a Pure Gluon Shower for Dark Sector Searches

Speaker: Caleb Gemmell (University of Toronto)

Caleb_Gemmell_LLPX.pdf

56 Revisiting the scotogenic model with scalar dark matter

Speaker: Ivania Maturana Ávila (Universidad Adolfo Ibáñez)

talk_LLP_workshop.pdf

57 On long-lived electroweak-singlet coloured scalars

Speaker: Christian Preuss (ETH Zürich)

58 Indirect detection of long-lived particles via a less-simplified dark Higgs portal

Speaker: Krzysztof Jodlowski

Jodlowski_LLPX.pdf

Coffee

Lightning round / new ideas: Session 5

Conveners: José Francisco Zurita (IFIC - Univ. of Valencia and CSIC (ES)), Margaret Susan Lutz (Tel Aviv University (IL))

Recording

59 Constraining Neutrino Magnetic Moments at the FPF

Speaker: Roshan Mammen Abraham (Oklahoma State University)

NMMatFPF_LLPX_roshan.pdf

60 Jet Timing

Speaker: Wen Han Chiu

Jet Timing Wen Han Chiu LLPX.pdf

61 Search for new light particles using MeV photon beam at the ILC

Speaker: Hajime Fukuda

ilc_lsw.pdf

Coffee

LHC LLP Working Group [cancelled]