Search for neutrinoless decays tau -> 3l

TL;DR

This study searched for neutrinoless tau decays into three leptons using Belle data, setting upper limits on branching fractions due to no significant signal observed.

Contribution

First search for neutrinoless tau -> 3l decays using Belle data, establishing new upper limits on branching fractions.

Findings

No significant signal observed.

Upper limits on branching fractions are set between 1.9 and 3.5 x 10^{-7}.

Results constrain models predicting neutrinoless tau decays.

Abstract

We have searched for neutrinoless tau lepton decays into three charged leptons using an 87.1 fb^{-1} data sample collected with the Belle detector at the KEKB e^+e^- collider. Since the number of signal candidate events is compatible with that expected from the background, we set 90% confidence level upper limits on the branching fractions in the range (1.9-3.5) x 10^{-7} for various decay modes tau -> l l l where l represents e or mu.