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 ${\tau }^{-}\to {\mu }^{-}{\nu }_{\tau }\overline{{\nu }_{\mu }}\gamma$ 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.

4 pages, two figures