Probing lepton flavour violation via neutrinoless τ → 3μ decays with the ATLAS detector

Abstract

This article presents the sensitivity of theATLAS experiment to the lepton-flavour-violating decays of τ → 3μ. A method utilising the production of τ leptons via W → τν decays is used. This method is applied to the sample of 20.3 fb<SUP>-1</SUP> of <i>pp</i> collision data at a centre-of-mass energy of 8 TeV collected by the ATLAS experiment at the LHC in 2012. No event is observed passing the selection criteria,and the observed (expected) upper limit on the τ lepton branching fraction into three muons, Br(τ → 3μ), is 3.76 × 10<SUP>-7</SUP> (3.94 × 10<SUP>-7</SUP>) at 90 % confidence level.