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 using Belle data, finding no evidence and setting more stringent upper limits on the branching fractions than previous experiments.

Contribution

The paper provides the first search for these specific tau decays with improved upper limits, enhancing constraints on lepton flavor violation models.

Findings

No signal observed in either decay mode.

Upper limits on branching fractions are set at 5.6×10⁻⁸ and 4.9×10⁻⁸.

Limits improve previous bounds by factors of 16 and 19.

Abstract

We have searched for the lepton flavor violating decays $\tau^-\to \ell^-\ks$ ($\ell = e {or} \mu$), 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: ${\cal{B}}(\tau^-\to e^-\ks) < 5.6\times 10^{-8}$ and ${\cal{B}}(\tau^-\to \mu^-\ks) < 4.9\times 10^{-8}$ at the 90% confidence level. These results improve the previously published limits set by the CLEO collaboration by factors of 16 and 19, respectively.