Observations on the radiative corrections to pion beta-decay
  We find that, in the local V-A theory, the radiative corrections to pion beta-decay involving the weak vector current, when evaluated in the current algebra (CA) formulation in which quarks are the fundamental underlying fields, show a small difference with the more elementary calculations based directly on the pion fields. We show that this difference arises from a specific short-distance effect that depends on the algebra satisfied by the weak and electromagnetic currents. On the other hand, we present a simple theoretical argument that concludes that this difference does not occur when the CA formulation is compared with the chiral perturbation theory (chiPT) approach. Comparisons with previous studies, and with a more recent calculation based on chiPT, are included. We also briefly review the important differences between the results in the local V-A theory and the Standard Model. 
M. Passera, K. Philippides, A. Sirlin
hep-ph hep-ex