Search for neutrinoless decays tau -> lhh and tau -> lV0

TL;DR

This study searched for neutrinoless tau decays into specific lepton-hadron and lepton-vector meson final states using Belle data, setting upper limits on their branching fractions due to no observed excess over background.

Contribution

First search for neutrinoless tau decays into lhh and lV0 modes using Belle data, establishing new upper limits on their branching fractions.

Findings

No significant excess observed over background.

Upper limits on branching fractions range from 1.6 to 8.0 x 10^-7.

Results constrain models predicting neutrinoless tau decays.

Abstract

We have searched for neutrinoless tau lepton decays into l h h or l V0, where l stands for an electron or muon, h for a charged light hadron, pi or K, and V0 for a neutral vector meson, rho, K*(892) and phi, using a 158 /fb data sample collected with the Belle detector at the KEKB e+e- collider. Since the number of events observed are consistent with the expected background, we set upper limits on the branching fractions in the range of 1.6-8.0 x 10-7 for various decay modes at the 90% confidence level.