Search for vector-like leptons coupling to first- and second-generation Standard Model leptons in pp collisions at SQUARE ROOTs = 13 TeV with the ATLAS detector

Abstract

A search for pair production of vector-like leptons coupling to first- and secondgenerationStandard Model leptons is presented. The search is based on a dataset ofproton-proton collisions at SQUARE ROOTs = 13TeV recorded with the ATLAS detector during Run 2 ofthe Large Hadron Collider, corresponding to an integrated luminosity of 140 fb-1. Events arecategorised depending on the flavour and multiplicity of leptons (electrons or muons), as wellas on the scores of a deep neural network targeting particular signal topologies accordingto the decay modes of the vector-like leptons. In each of the signal regions, the scalarsum of the transverse momentum of the leptons and the missing transverse momentum isanalysed. The main background processes are estimated using dedicated control regions in asimultaneous fit with the signal regions to data. No significant excess above the StandardModel background expectation is observed and limits are set at 95% confidence level on theproduction cross-sections of vector-like electrons and muons as a function of the vector-likelepton mass, separately for SU(2) doublet and singlet scenarios. The resulting mass lowerlimits are 1220 GeV (1270 GeV) and 320 GeV (400 GeV) for vector-like electrons (muons) inthe doublet and singlet scenarios, respectively.