Search for Lepton-Flavor Violation in the Decay ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$

Search for Lepton-Flavor Violation in the Decay $τ^{-} \to ℓ^{-} ℓ^{+} ℓ^{-}$

B. Aubert et al. (BABAR Collaboration)

Phys. Rev. Lett. 92, 121801 – Published 26 March 2004

Abstract

A search for the lepton-flavor-violating decay of the tau into three charged leptons has been performed using $91.5 {fb}^{- 1}$ of data collected at an $e^{+} e^{-}$ center-of-mass energy around $10.58 GeV$ with the BABAR detector at the SLAC storage ring PEP-II. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range $(1 - 3) \times 10^{- 7}$ at 90% confidence level.