Radiative Corrections and the Universality of the Weak Interactions

We review the radiative corrections to superallowed Fermi transitions and neutron β decay in the Standard Model, and their relevance for the universality of the Weak Interactions. Radiative Corrections and the Universality of the Weak Interactions Alberto Sirlin The study of radiative corrections (R.C.) to μ and β decays has played an important role in the analysis of weak interactions before and after the emergence of the Standard Model (SM). In the framework of the local V-A theory that preceded the SM, the R.C. to μ decay are convergent, to first order in GF and all orders in α, after charge and mass renormalization [1]. The corrections to the electron spectrum in μ decay are large and play an important role in verifying that the parameters ρ and δ equal 3/4, a major prediction of the V-A theory [2]. The expression for the μ lifetime is