Session B13: Beyond the Standard Model Searches at the LHC I

Live

A search for dijet resonances in events with identified leptons is performed using data collected in $pp$ collisions at $ \sqrt s=13$TeV by the ATLAS detector between 2015 and 2018, corresponding to an integrated luminosity of 139 $fb^{-1}$. We examine the dijet invariant mass distribution in the range of 0.22 $< m_{jj} < $ 6.3 TeV. The analysis probes much lower mjj than traditional inclusive dijet searches and is sensitive to a large range of new physics models with a final-state lepton. This talk summarizes the latest search results that are interpolated in the context of a charged Higgs decaying to a top and bottom quarks.   

Live

This presentation presents a study that examines the CMS experiment's final prospects for exploring the degenerate corridor of top squark and neutralino masses. The sensitivity study employs Monte Carlo samples that simulate conditions at the High Luminosity Large Hadron Collider, i.e. a 14 TeV center of mass energy and 200 pile up conditions, corresponding to an integrated luminosity of 3 ab$-$1. Working with dilepton events, we analyze the $\Delta \varphi $ll variable, the difference in azimuthal angle $\varphi $ between the two decay leptons in the laboratory frame, to set limits on the stop decay cross-sections.   

Live

Many extensions to the Standard Model include long lived particles (LLPs), which are metastable to the ATLAS detector. This talk presents results from a search for two leptons with high impact parameter in the in $pp$ collisions at $\sqrt{s}=$ 13 TeV with the ATLAS detector at the LHC using the full Run 2 dataset. Such a signature could be the result of a gauge mediated supersymmetry breaking (GMSB) slepton decaying into a gravitino and standard model lepton, last searched for in OPAL at LEP. Results of this analysis are presented.   

Live

The production of a top quark pair with a photon is sensitive to beyond the standard model physics such as a top quark electric dipole, or top quark production charge asymmetry. We report the cross section for the production of a top quark pair with a photon $\sigma(\text{tt}\gamma)$, and the ratio of cross sections $\sigma(\text{tt}\gamma)$/$\sigma(\text{tt})$ using the Run 2 data of the CMS experiment. The analysis is carried out in the semileptonic electron and muon decay channel. Backgrounds are constrained by extensive studies in control regions.   

Live

A search for top squarks is presented based on proton-proton collision events containing hadronically decaying top quarks, no leptons, and an imbalance in transverse momentum. The data used were collected by the CMS detector at the CERN LHC with a center-of-mass energy of 13 TeV during CMS Run 2 (2016-2018) corresponding to an integrated luminosity of 137 inv. fb. Heavy object taggers were developed for identifying boosted top quarks, boosted W bosons and resolved top quarks using deep learning techniques. Search regions are defined in terms of the multiplicity of bottom quark jets, top quark and W jet candidates, missing transverse momentum, and the scalar sum of jet transverse momenta. This presentation will focus on the major background from leptonic decays of the W boson due to leptons failing the lepton selection requirements.   

Live

A search for hadronically-decaying top squarks is presented, based on an integrated luminosity of 137 /fb of proton-proton collision data recorded by the CMS experiment with a center-of-mass energy of 13 TeV. Search regions are defined in terms of the multiplicity of bottom quark jets, top quark and W boson candidates, missing transverse momentum, and the scalar sum of jet transverse momenta. Three backgrounds of the analysis will be discussed here: the QCD, irreducible TTZ, and rare backgrounds. The results include limits for both direct and gluino-mediated top squark production.   

Live

A search for hadronically decaying top squarks is presented using three years of proton-proton collisions at center-of-mass energy of 13 TeV recorded by the CMS experiment, corresponding to an integrated luminosity of 137 inv. fb. The light top squark is expected with mass around 1\textasciitilde 2 TeV in natural supersymmetric models, therefore accessible at the LHC. This search looks for a final state with hadronically decaying top quarks, and large imbalance in transverse momentum. While there are several backgrounds present, one of the largest and irreducible backgrounds comes from Z bosons decaying to two neutrinos, with a significant branching ratio of 0.2. Two methods for estimating the Z invisible background will be discussed.   

Not Participating

Some new physics scenarios beyond the Standard Model predict the decay of the Higgs boson to supersymmetric particles involving axion-like pesudoscalars. In this talk I discuss progress on a search for exotic Higgs decays to supersymmetric particles and pseudoscalars in vector boson fusion (VBF) events in $pp$ collisions at $\sqrt{s}=$ 13 TeV with the ATLAS detector.   

Not Participating

A search for exotic decays of the Higgs boson $h$ to a pair of light pseudoscalars $a$, where each pseudoscalar decays to a bottom quark-antiquark pair, $h\rightarrow aa\rightarrow b\overline{b}b\overline{b}$, is presented. Such signatures are predicted by many models for physics beyond the standard model, such as next-to-minimal supersymmetry and two-Higgs-doublet models with an additional scalar singlet. This analysis is based on the data set of proton-proton collisions at 13 TeV collected by the CMS experiment at the CERN LHC in 2016, 2017, and 2018, corresponding to an integrated luminosity of 137.1 fb$^{-1}$. The search is performed in the Higgs boson production channel in which it is produced in association with W or Z boson, utilizing the charged leptons from leptonic decays of the W or Z boson to suppress the standard model background.