Improved Limits on the Lepton-Flavor Violating Decays tau- --> l-l+l-

TL;DR

This paper reports a search for lepton-flavor violating tau decays into three charged leptons, setting new upper limits on their branching fractions using data from the BaBar experiment.

Contribution

First search for these specific tau decay modes with improved upper limits on branching fractions using a large dataset.

Findings

No significant signal observed in any decay mode.

Upper limits on branching fractions are set between 4 and 8 x 10^{-8}.

Results improve constraints on lepton-flavor violation models.

Abstract

A search for the neutrinoless, lepton-flavor violating decay of the tau lepton into three charged leptons has been performed using 376 fb^{-1} of data collected at an e^+e^- center-of-mass energy around 10.58 GeV with the BaBar detector at the PEP-II storage rings. 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 (4-8) x 10^{-8} at 90% confidence level.