Radiative two-pion decay of the tau lepton

Abstract

We consider the bremsstrahlung and model-dependent contributions to the radiative decay ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\nu}}_{\ensuremath{\tau}}\ensuremath{\gamma}$ in the context of a meson dominance model. We focus on several observables related to this decay, including the branching ratio and the photon and di-pion spectra. Particular attention is paid to the sensitivity of different observables upon the effects of model-dependent contributions and of the magnetic dipole moment of the ${\ensuremath{\rho}}^{\ensuremath{-}}(770)$ vector meson. Important numerical differences are found with respect to results obtained in the framework of chiral perturbation theory.