Rare tau decays at Belle

TL;DR

This paper reports a search for rare tau lepton decays that violate lepton flavor, lepton number, and baryon number, using the largest dataset from Belle, achieving sensitivity to branching fractions around 10^{-8}.

Contribution

First search for multiple rare tau decays with improved sensitivity using the Belle detector and the largest available data sample.

Findings

No significant signals observed for the targeted decays.

Branching fraction sensitivities improved to the order of 10^{-8}.

Results set new upper limits on rare tau decay modes.

Abstract

We report results of a search for tau lepton decays strongly suppressed in the Standard Model based on the world-largest data sample accumulated with the Belle detector at the KEKB asymmetric-energy e+e- collider. The decays include: lepton flavor and lepton number violating tau decays into a lepton (e or mu) and two charged mesons (K or pi) as well as lepton and baryon number violating tau decays into a Lambda and a charged meson (K or pi). The sensitivity to the branching fractions is significantly improved compared to our previous results and reaches O(10^{-8}).