Search for Neutrinoless tau Decays Involving the K_S^0 Meson

TL;DR

This study searched for rare lepton flavor violating tau decays involving K_S^0 mesons using data from the CLEO detector, setting new upper limits on their branching fractions due to no observed signals.

Contribution

It provides the first upper limits on three-body tau decays involving K_S^0 and improves existing limits on two-body decays, enhancing constraints on new physics models.

Findings

No evidence for lepton flavor violating tau decays was observed.

Set new upper limits on branching fractions for tau decays involving K_S^0.

First upper limits established for three-body tau decays with K_S^0.

Abstract

We have searched for lepton flavor violating decays of the tau lepton with one or two KS0 mesons in the final state. The data used in the search were collected with the CLEO II and II.V detectors at the Cornell Electron Storage Ring (CESR) and correspond to an integrated luminosity of 13.9 fb^-1 at the Upsilon(4S) resonance. No evidence for signals were found, therefore we have set 90% confidence level (C.L.) upper limits on the branching fractions B(tau -> e KS0) < 9.1e-7, B(tau -> mu KS0) < 9.5e-7, B(tau -> e 2KS0) < 2.2e-6, and B(tau -> mu 2KS0) < 3.4e-6. These represent significantly improved upper limits on the two-body decays and first upper limits on the three-body decays.