Search for Lepton Flavor Violating tau- Decays into \ell-K0s and \ell-K0sK0s

TL;DR

This study searched for lepton flavor violating tau decays into specific mesons using a large data sample, found no evidence, and established new upper limits on their branching fractions, constraining new physics models.

Contribution

First search for tau lepton decays into s mesons with stringent upper limits, improving constraints on lepton flavor violation.

Findings

No evidence of the decay modes was observed.

Upper limits on branching fractions were set at 10^-8 levels.

Results constrain theories predicting lepton flavor violation.

Abstract

We have searched for the lepton-flavor-violating decays tau- -> ell-K0s and ell-K0sK0s (ell = e or mu), using a data sample of 671 fb^-1 collected with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. No evidence for a signal was found in any of the decay modes, and we set the following upper limits for the branching fractions: B(tau^- -> e^-K0s) < 2.6 x 10^-8, B(tau^- -> \mu^-K0s) < 2.3 x 10^-8, B(tau^- -> e^-K0sK0s) < 7.1 x 10^-8 and B(tau^- -> mu^-K0sK0s) < 8.0 x 10^-8 at the 90% confidence level.