The pionic beta decay in chiral perturbation theory

Within the framework of chiral perturbation theory with virtual photons and leptons, we present an updated analysis of the pionic beta decay including all electromagnetic contributions of order e 2 p 2 . We discuss the extraction of the Cabibbo-Kobayashi-Maskawa matrix element |V ud | from the experimental data. The method employed here is consistent with the analogous treatment of the \(K_{\ell 3}\) decays and the determination of |V us |.