Search for Lepton Flavor Violating tau- Decays Including with a K0s Meson

TL;DR

This study searched for lepton flavor violating tau decays involving a K0s meson, setting new upper limits on their branching fractions with no evidence of such decays observed.

Contribution

The paper provides the most stringent upper limits to date on tau lepton flavor violating decays involving a K0s meson, improving previous bounds significantly.

Findings

No evidence for tau- -> e-K0s or tau- -> mu-K0s decays was found.

Upper limits on branching fractions were set at 5.6 x 10^-8 and 4.9 x 10^-8.

Results improve previous limits by factors of 16 and 19.

Abstract

We have searched for the tau lepton flavor violating decays tau- -> l-K0s (l = e or mu), using a data sample of 281 fb^-1 collected with the Belle detector at the KEKB e+e- asymmetric-energy collider. No evidence for a signal was found in either of the decay modes, and we set the following upper limits for the branching fractions: B(tau- -> e-K0s) < 5.6 * 10^-8 and B(tau- -> m^-K0s) < 4.9 * 10^-8 at the 90% confidence level. These results are improvements by factors of 16 and 19, respectively, compared with previously published limits from CLEO.