Search for the Decay of a Tau Lepton to Three Muons in Data from the Compact Muon Solenoid Experiment at the Large Hadron Collider

Abstract

We search for the flavor-violating decays τ\(^{−}\) → µ\(^{−}\)µ\(^{+}\)µ\(^{−}\) and τ\(^{+}\) → µ\(^{+}\)µ\(^{-}\)µ\(^{+}\) in data from the CMS experiment at the LHC at √ s = 8 TeV. This search focuses on tau leptons that originate from decays of a W boson (W\(^{−}\) → τ\(^{−}\)ν¯\(_{τ}\) and W\(^{+}\) → τ\(^{+}\)ν\(_{τ}\) ). Using a dataset that we expect to include 8.33 × 107 tau leptons from W decays, we set a limit on the branching fraction of B(τ → 3µ) < 9.85 × 10\(^{-7}\) at a 90% confidence level and B(τ → 3µ) < 1.29 × 10\(^{-6}\) at a 95% confidence level.