Radiativeπ−eDecay

Under the assumption that the pion decay into an electron and a neutrino is forbidden or partially forbidden, the probability for a pion to decay into an electron, a neutrino, and a photon is considered under general assumptions as to the intermediate state. The spectra of the electron energy in this radiative decay are obtained for the various types of the interaction between the particles in the intermediate state and the leptons in the final state. The total probability of the radiative decay is of the order of ${10}^{-5\mathrm{}}$ per $\pi -\mu$ decay, except in the case of the scalar interaction where both the radiationless and radiative decays are forbidden.