Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session Y15: Collider and BSM VI |
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Sponsoring Units: DPF Chair: Fernanda Psihas, University of Texas, Austin Room: Sheraton Plaza Court 4 |
Tuesday, April 16, 2019 1:30PM - 1:42PM |
Y15.00001: Search for supersymmetry in the single-lepton final state using the sum of large jet masses Alex Dorsett, Jeffrey D Richman, David D Stuart A search is described for supersymmetric particles in proton-proton collisions in the final state with a single, high transverse momentum lepton; multiple jets, including at least one b-tagged jet; and large missing transverse momentum. The search uses the complete Run 2 dataset of proton-proton collisions at √s = 13 TeV collected by the CMS experiment from 2016 to 2018, corresponding to a total integrated luminosity of 136 ifb. The search focuses on processes leading to high jet multiplicities, such as gluino pair production with g->ttχ. The quantity MJ, defined as the sum of the masses of the large-radius jets in the event, is used in conjunction with other kinematic variables to provide discrimination between signal and background and as a key part of the background estimation method. The analysis is sensitive to models of supersymmetry with gluino pair production followed by three-body decays into top quarks and neutrinos. The search also probes models with two-body gluino decays producing on-shell top squarks. |
Tuesday, April 16, 2019 1:42PM - 1:54PM |
Y15.00002: Search for long-lived particles decaying into displaced jets Jingyu Luo The existence of long-lived particles (LLPs) is very generic in many beyond standard model scenarios. When LLPs decay to final states containing jets, displaced jet signatures will emerge. We present a search for displaced jets, based on proton-proton collision data collected with the CMS experiment at a center-of-mass energy of 13 TeV in 2016, corresponding to an integrated luminosity of 35.9 fb-1. The search utilizes the striking properties of displaced tracks and displaced vertices to identify jets arising from long-lived particles, and is sensitive to a wide range of models. |
Tuesday, April 16, 2019 1:54PM - 2:06PM |
Y15.00003: Supersymmetry discovery potential at HL-LHC and HE-LHC Amin Aboubrahim The discovery of the Higgs boson at ∼125 GeV indicates that the size of weak scale supersymmetry is higher than what was perceived in the pre-Higgs boson discovery era and lies in the several TeV region. This makes the discovery of supersymmetry more challenging and argues for hadron colliders beyond LHC at 14 TeV. A possibility recently proposed is the high energy LHC (HE-LHC) with significantly higher luminosity than at the HL-LHC. In this work we investigate the potential of HE-LHC for the discovery of supersymmetry in three categories of particle production: gluinos, electroweakinos and heavy charged Higgs. We study a class of supergravity unified models under the Higgs boson mass and the dark matter relic density constraints and compare the analysis with the potential reach of the HL-LHC. A set of benchmarks is presented which are beyond the discovery potential of HL-LHC but are discoverable at HE-LHC. For comparison, we study model points at HE-LHC which are also discoverable at HL-LHC. For these model points, it is shown [PRD 98, 015009 (2018) and PRD 98, 095024 (2018)] that the runtime required for discovery is greatly reduced at HE-LHC in comparison to HL-LHC indicating that the HE-LHC possibility should be seriously pursued. |
Tuesday, April 16, 2019 2:06PM - 2:18PM |
Y15.00004: Searching for Ultra Long-Lived Particles with MATHUSLA Mason Proffitt Long-lived particles (LLPs) are a feature of many theories beyond the Standard Model and would be generically produced in exotic decays of the Higgs boson. No known search strategy with current experiments will be able to observe the decay of neutral LLPs with masses above ~1 GeV at lifetimes near the upper limit set by Big Bang nucleosynthesis (cτ ~ 10⁷ m). The proposed MATHUSLA experiment would implement existing technology into a new detector at ground level above one of the interaction points (IPs) of the Large Hadron Collider (LHC) by the start of its high luminosity run in 2026. A small-scale MATHUSLA test stand was installed on the surface above the ATLAS detector at IP 1 of the LHC during part of its operation in 2017 and 2018. We describe this test stand, designed to study the background rates of downward-going muons originating from cosmic rays and upward-going muons created in LHC proton-proton collisions, as well as the ability of tracking to distinguish between these two sources, and present the initial results. |
Tuesday, April 16, 2019 2:18PM - 2:30PM |
Y15.00005: Searching for axion-like particles in light-by-light scattering with proton tagging at the Large Hadron Collider Cristian X Baldenegro Barrera The existence of pseudoscalars weakly coupled to particles from the Standard Model of particle physics, known as axion-like particles (ALP), would induce anomalous scattering of light-by-light. Searching for these particles relying only on their coupling to the electromagnetic field is challenging. This process can be probed at the Large Hadron Collider (LHC) in production of photon pairs in proton-proton where the protons remain intact after the collision and have lost a fraction of their original longitudinal momentum due to coherent photon exchanges (pp -> p γγ p), and are tagged using dedicated forward proton spectrometers installed at the LHC. We estimate the expected sensitivity on the ALP--photon coupling for a wide range of masses. We show that the proposed search is competitive and complementary to other collider bounds for masses above 600 GeV, especially for resonant ALP production between 600 GeV and 2 TeV. |
Tuesday, April 16, 2019 2:30PM - 2:42PM |
Y15.00006: Forward Physics with intact protons at the LHC Cristian Baldenegro, Christophe Royon We will first describe how forward physics can lead to a better insight on the proton structure in terms of quarks and gluons at the LHC in the high gluon density regime. We will also discuss how detecting protons at the LHC leads to unprecedented sensitivities to Axion Like Particles and quartic photon anomalous coupling increasing the usual sensitivities to couplings by more than three orders of magnitude at the LHC. |
Tuesday, April 16, 2019 2:42PM - 2:54PM |
Y15.00007: A search for pair production of new light bosons decaying into muons Wei Shi A search for new light bosons decaying into muon pairs is presented using a data sample corresponding to an integrated luminosity of 35.9 fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector at the CERN LHC. The search is model independent, only requiring the pair production of a new light boson and its subsequent decay to a pair of muons. No significant deviation from the predicted background is observed. A model independent limit is set on the product of the production cross section times branching fraction to dimuons squared times acceptance as a function of new light boson mass. This limit varies between 0.16 and 0.45 fb over a range of new light boson masses from 0.25 to 8.5 GeV. It is then interpreted in the context of the next-to-minimal supersymmetric standard model and a dark supersymmetry model that allows for nonnegligible light boson lifetimes. In both cases, there is significant improvement over previously published limits. |
Tuesday, April 16, 2019 2:54PM - 3:06PM |
Y15.00008: Searches for dark matter mediators with dijet final states in pp collisions at √s = 13 TeV with the ATLAS detector at the LHC Kathleen Whalen, David M Strom, Antonio Boveia, Emma Tolley The ATLAS experiment at the Large Hadron Collider (LHC) has a rich programme of searches for dark matter, encompassing a wide range of models and signatures. Many models of dark matter feature a new particle that mediates the interaction between Standard Model particles and dark matter; this mediator particle could decay to quarks and gluons, producing a dijet resonance signature in the detector. With the unprecedented high luminosity delivered by the LHC, detector readout and data storage limitations restrict conventional searches for dijet resonances to masses of about 1 TeV or higher. In order to extend the search range to lower masses on the order of 100 GeV and probe weaker couplings, the ATLAS experiment employs a range of novel trigger and analysis strategies. These include searches for dijet resonances produced in association with a photon or jet from initial-state radiation (dijet+ISR), and the trigger-level analysis (TLA), which records only trigger-level jet objects instead of the full detector information, thus permitting the use of lower jet trigger thresholds and increased recording rates, with minimal impact on the total output bandwidth. This talk will present the most recent results from the Run 2 dijet searches using these techniques. |
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