The anomalous four-point interaction in the radiative leptonic $\tau$ decay

Abstract

As one of the extensions of the Standard Model, we investigate the anomalous four-point $\tau-W-\nu_\tau-\gamma$ scalar- and tensor-type interactions, which originate from the gauge invariant dimension-five operators. The coupling constants are constrained by the measured branching ratio of the $\tau^- \rightarrow \mu^- \nu_{\tau} \bar{\nu_\mu} \gamma$ decay: $-4.9<\kappa_\tau^S<9.4$ and $-1.4<\kappa_\tau^T<2.8$ at the 95% confidence level for the scalar and tensor interactions, respectively.