Rare decays of tau-lepton

Abstract

We have searched for the Lepton Flavor Violating decays τ^–→μ^–γ and τ^–→μ^–η using ~85 fb^–1 of data accumulated by the Belle detector at KEKB, and attained preliminary upper limits for the branching fraction Br(τ^–→μ^–γ) < 3.2× 10^–7 and Br(τ^–→μ^–η) < 3.4 × 10^–7, respectively, at the 90% confidence level. These are the first data that reach to the sensitivity of 10^–7 level, and provide some constraints on the parameter spaces of $\tan\beta$ vs. SUSY mass and $\tan\beta$ vs. Higgs mass.

PACS: number(s) 13.35.Dx, 11.30.Fs, 14.60.Fg