Search for heavy lepton resonances decaying to a \(Z\) boson and a lepton in \(pp\) collisions at \(\sqrt{s}=8\) TeV with the ATLAS detector

Abstract

A search for heavy leptons decaying to a \(Z\) boson and an electron or a muon is presented. The search is based on \(pp\) collision data taken at \(\sqrt{s}=8\) TeV by the ATLAS experiment at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb\(^{-1}\), Three high-transverse-momentum electrons or muons are selected, with two of them required to be consistent with originating from a \(Z\) boson decay. No significant excess above Standard Model background predictions is observed, and 95% confidence level limits on the production cross section of high-mass trilepton resonances are derived. The results are interpreted in the context of vector-like lepton and type-III seesaw models. For the vector-like lepton model, most heavy lepton mass values in the range 114-176 GeV are excluded. For the type-III seesaw model, most mass values in the range 100-468 GeV are excluded.