Analysis of radiative pion decay π-→e-νγ

We give a quantitative account of radiative pion decays. By the chiral structure of the interaction and the fact of the low mass ratio between an electron and a pion, one can suppress the inner-bremsstrahlung contribution and decays with the emission of a negative-helicity electron. By this observation, we examine a way of determining the value of the structure-dependent parameter γ, giving particular attention to the decay spectra with this electron helicity. We also investigate the effects of a neutrino mass in this process