Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X19: Searches for Long-Lived BSM ParticlesLive
|
Hide Abstracts |
Sponsoring Units: DPF Chair: Zhen Liu, University of Minnesota |
Tuesday, April 20, 2021 10:45AM - 10:57AM Live |
X19.00001: Search for long-lived particles decaying into two muons in proton-proton collisions at sqrt(s)=13TeV using the CMS scouting data sets Hardik Routray A search for displaced dimuon resonances is performed using proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment at the LHC in 2017–2018, corresponding to an integrated luminosity of 101.3 inv. fb. The data sets used in this search were collected using a dedicated dimuon scouting trigger stream, in order to explore otherwise inaccessible phase space at low dimuon mass (down to 0.21 GeV) and non-zero displacement (0-11cm) from the interaction point. Constraints are set on two models of physics beyond the Standard Model: one model where a Higgs boson decays into a pair of long-lived dark photons, and the other model where a B hadron decays via a long-lived scalar particle. A number of mass and lifetime hypotheses are considered for the involved long-lived particles, and one long-lived particle is required to decay into a pair of muons. Model-independent constraints are also set. [Preview Abstract] |
Tuesday, April 20, 2021 10:57AM - 11:09AM Live |
X19.00002: Search for Neutral Long-lived Particles Decaying in the CMS Endcap Muon System Christina Wang We present a first search at CMS that uses the endcap muon system (EMS) as a sampling calorimeter to identify hadronic showers produced by decays of long-lived particles (LLPs). The EMS comprises of gas ionization Cathode Strip Chambers (CSCs) sandwiched within the steel material of the magnetic flux-return yoke. LLPs that decay to hadrons within the EMS induce hadronic and electromagnetic showers resulting in localized, high-multiplicity CSC hit showers that are identified with a novel reconstruction technique. The unique design of steel flux-return yoke in the CMS detector provides exceptional shielding from SM background that dominates existing LLP searches. The search yields competitive sensitivity for proper lifetime from 0.1m to 1000m with 137 fb$^{-1}$ of proton-proton collisions at 13TeV recorded during 2016-2018 at the CMS detector. [Preview Abstract] |
Tuesday, April 20, 2021 11:09AM - 11:21AM Live |
X19.00003: A search for long-lived neutral particles that decay into a pair of muons in proton-proton collisions at sqrt(s)=13 TeV in the CMS detector William Nash A search for long lived neutral particles that decay into a pair of muons is performed using proton-proton collisions at sqrt(s)=13 TeV recorded within the CMS detector at the LHC. An integrated luminosity of 97.6 fb-1 is used to perform the search, collected during 2016 and 2018 data taking runs. The search is intended to be model independent and is sensitive to displacements ranging from several hundred microns to several meters and masses above 10 GeV. Results are interpreted in the context of the Hidden Abelian Higgs Model, where a Higgs boson decays into a pair of dark photons, and a model in which the displaced particle is a neutral scalar. [Preview Abstract] |
Tuesday, April 20, 2021 11:21AM - 11:33AM Live |
X19.00004: Search for Long-lived Particles with Trackless Jets and Missing Transverse Energy (ECAL Timing) at LHC with CMS Detector Jiajing Mao We present a search for long-lived particles (LLPs) that decay to Higgs or Higgs-like bosons using a trackless and delayed jet signature. LLP decays that occur in the calorimeter systems will produce a jet object with no associated tracks and significant delays in arrival time. We combine the time stamps recorded in the CMS ECAL to reconstruct the arrival time of jets. Machine learning techniques are used to develop a trackless and delayed jet tagger based on deep neural networks. The results are based on data from proton-proton collisions at the Large Hadron Collider (LHC) at a center-of-mass energy of 13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 137 fb-1. We achieve the best sensitivity for LLP decays that occur between a few tens of centimeters to about one meter from the interaction point. [Preview Abstract] |
Tuesday, April 20, 2021 11:33AM - 11:45AM Live |
X19.00005: The Search for Lightly Ionizing Particles in the Large Underground Xenon Experiment Paul Terman The question of the nature of dark matter has become increasingly puzzling as more experiments exclude larger portions of the favored WIMP parameter space. Previous theoretical work has suggested the existence of Lightly Ionizing Particles (LIPs) with charge $e \cdot f$, where $e$ is the electron charge and $f < 1$. We seek to utilize data from the first underground WIMP search of the Large Underground Xenon (LUX) experiment, using a dual-phase xenon Time Projection Chamber (TPC), to search for LIPs in the range $f = 0.01$ to $0.3$. To accomplish the aforementioned search new methods of Geant4 based simulation and data processing have been implemented, including the first use of pulse $chopping$ for merged signals in a dual-phase TPC. Traditional event selection criteria are compared to newer Boosted Decision Tree (BDT) machine learning-based event selections to place new, world-leading limits on LIP flux. [Preview Abstract] |
Tuesday, April 20, 2021 11:45AM - 11:57AM Live |
X19.00006: Spin-Dependent Fifth-Force Search Using 1 kHz Mechanical Oscillators Caleb Hughes, Josh Long Exotic interactions arise in many theoretical frameworks attempting to unify General Relativity and quantum mechanics. We describe an experimental search with sensitivity to fifteen exotic spin-dependent potentials in the sub-millimeter range, using planar resonant test masses with operational frequencies near 1 kHz. The test masses have been augmented with a polarized ferrimagnetic material which exhibits temperature-dependent orbital cancellation of the magnetism associated with the electron spins, substantially reducing the magnetic backgrounds. Cancellation is maximal (ideally perfect) at the compensation temperature near 225 K. A complete apparatus, designed to make optimal use of the ferrimagnet, has been tested. The apparatus has been surrounded with a radiative shield containing a liquid nitrogen reservoir for cooling. To assess the remnant magnetization during cooldown and locate the compensation temperature, the apparatus contains a set of coils to drive the detector with a resonant magnetic gradient. At 223.7 K, the magnetic driving force is reduced by at least a factor of 240 relative to its room temperature value. We describe this operation and discuss the projected sensitivity to exotic potentials. [Preview Abstract] |
Tuesday, April 20, 2021 11:57AM - 12:09PM Live |
X19.00007: Freeze-in Leptogenesis via Dark Matter Oscillations Justin Berman, Brian Shuve, David Tucker-Smith Models of freeze-in dark matter that incorporate two or more dark matter mass eigenstates below ~100 keV can simultaneously account for the observed baryon asymmetry, through the oscillations of the out-of-equilibrium dark matter particles. We consider the case in which the dark matter is produced by early-universe decays of electroweak-charged scalars, the lightest of which must be in the few-hundred GeV to TeV range to realize the observed dark matter and baryon densities. Using a network of quantum kinetic equations that describe dark matter production, annihilation, and oscillations, along with washout and spectator processes, we find that the minimal model, with two dark matter mass eigenstates and a single scalar, is tightly constrained. Including Yukawa couplings of the scalar beyond its interaction with the dark matter or adding one or more additional scalars significantly expands the viable parameter space, much of which has the lightest scalar being long-lived at colliders. We discuss the model’s discovery potential at the LHC along with other possible experimental probes. [Preview Abstract] |
Tuesday, April 20, 2021 12:09PM - 12:21PM Live |
X19.00008: The REDTOP Experiment Anna Mazzacane The peculiarity of the $\eta$ and $\eta'$ mesons is that all their quantum numbers are zero (as it occurs for the Higgs). This is a very rare occurrence in nature and strongly constrains the dynamics of those particles. Therefore their decays offer many opportunities for exploring Physics Beyond the Standard Model (BSM). REDTOP is a propose $\eta/\eta'$ factory which aims at detecting small deviations from the Standard Model by collecting a large event set from protons impinging on multiple fixed targets. The experiment will produce about $10^{13}~ \eta$ mesons or $10^{11}~ \eta'$ mesons corresponding to an increase of the existing world sample by four orders of magnitude. The experiment will investigate violations of discrete symmetries and will search for new weakly-coupled light particles in the MeV-GeV mass scale. It will also provide an opportunity to investigate several Standard Model predictions with unprecedented precision. The Collaboration has identified two different running modes (untagged and tagged) corresponding to different production mechanisms of $\eta$ and $\eta'$ mesons. The tagged mode offers the opportunity for discovering long-lived particles escaping the detector. The physics program, the accelerator systems and the detector for REDTOP are discussed. [Preview Abstract] |
Tuesday, April 20, 2021 12:21PM - 12:33PM Live |
X19.00009: Study of $\chi^{2}$ Metric Based Analysis Cut on Ultra Low Energy Spectrum of CUORE Data Rebecca Kowalski, Danielle Speller, Antonio Branca The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton-scale bolometer located at Gran Sasso National Laboratories in Assergi, Italy. To date, CUORE has collected over 1000 kg yr of exposure. Using the spectrum provided by the experiment’s bolometric detectors, we optimize for a selection of events at energies lower than typically used for CUORE beta-decay searches in an effort to increase sensitivity to dark matter candidates. This is done with a reduced $\chi^{2}$ metric available from the cubic-spline fit of pulses detected per bolometer (after applying the Optimum Filter and Optimum Trigger previously developed for use in CUORE) as a shape indicator of a good event. This metric was explored for CUORE-0 as a technique to increase the usable physics data at lower energies. However, these studies were performed for higher analysis thresholds than suitable for a dark matter search. Using a modified energy-dependent selection cut, we can improve the event selection as a function of energy, as opposed to relying on just the $\chi^{2}$ as was done previously. We investigate the impact on the quality of selected data in energies lower than 40keV. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700