First observation of the decay ${\tau }^{-}\to \varphi K^{-}{\nu }_{\tau }$

Abstract

We present the first observation of τ lepton decays to hadronic final states with a ϕ-meson. This analysis is based on 401 fb⁻¹ of data accumulated at the Belle experiment. The branching fraction obtained is $\mathcal{B}({\tau }^{-}\to \varphi K^{-}{\nu }_{\tau })=(4.05\pm 0.25\pm 0.26)\times {10}^{\mathrm{-5}}$.