Search for Lepton-Flavor Violation in the Decay $\tau^-\to\ell^-\ell^+\ell^-$

Abstract

A search for the lepton-flavor-violating decay of the tau into three charged leptons has been performed using $91.5 \mathrm{fb}^{-1}$ of data collected at an $e^+e^-$ center-of-mass energy of 10.58 GeV with the BaBar detector at the PEP-II storage ring. 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.