Electromagnetic radiative corrections to pionic beta decay π+ → π0e+νε

Pionic beta decay π+ → π0e+νe is analyzed in chiral perturbation theory with virtual photons and leptons. All electromagnetic corrections up to O(e2p2) are taken into account. Theoretical results are confronted with preliminary data from a PSI measurement and a value for the CKM matrix element vertical bar Vud vertical bar is given. Although the precision is presently still below the one of existing determinations of vertical bar Vud vertical bar, an analysis of pionic beta decay, based on a systematic treatment within a low-energy effective field theory, may become a useful alternative