Search for displaced leptons in SQUARE ROOTs = 13 TeV and 13.6 TeV pp collisions with the ATLAS detector

Abstract

A search for leptons displaced from the primary vertex is performed with the ATLAS detector at theLarge Hadron Collider. The search includes the full proton-proton collision dataset collected during Run 2at ffiffiffi sp1/4 13 TeV and a partial dataset collected during Run 3 in 2022-2023 at ffiffiffi sp1/4 13.6 TeV,corresponding to integrated luminosities of 140 fb-1 and 56.3 fb-1, respectively. Final states withdisplaced electrons or muons are considered, and novel triggers introduced in Run 3 are employed thatuse large impact parameter tracking to reconstruct displaced tracks with low momentum. In addition,photon reconstruction and multivariate techniques are employed to broaden the sensitivity to channels withlarge background rates or highly displaced electrons, respectively. The results are consistent with theStandard Model background expectations and are used to set model-independent limits on the productionof displaced electrons and muons. The analysis is also interpreted in the context of a gauge-mediatedsupersymmetry breaking model with pair-produced long-lived sleptons and a dark sector model with pairproducedchargino-like states. The results include 95% confidence level exclusions of selectrons withlifetimes from 4 ps to 60 ns and a mass of 150 GeV, and exclusions of selectrons, smuons, and staus with alifetime of 0.3 ns for masses up to 740, 830, and 440 GeV, respectively. Dark charginos with masses up to380 GeVare excluded for a mass difference with the neutral state of 40 GeV, and mass differences down to17 GeV are excluded for dark charginos with a 100 GeV mass.