Limits on tau Lepton-Flavor Violating Decays in three charged leptons

TL;DR

This paper reports a search for tau lepton decays violating lepton flavor into three charged leptons, setting upper limits on their occurrence rates with no significant signal observed.

Contribution

First search for neutrinoless, lepton-flavor violating tau decays into three charged leptons using a large dataset, establishing new upper limits on branching fractions.

Findings

No significant excess of events observed.

Upper limits on branching fractions between 1.8 and 3.3 x 10^-8.

Results constrain theories predicting lepton-flavor violation.

Abstract

A search for the neutrinoless, lepton-flavor violating decay of the tau lepton into three charged leptons has been performed using an integrated luminosity of 468 fb^-1 collected with the BABAR detector at the PEP-II collider. 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 (1.8-3.3) X 10^-8 at 90% confidence level.