Effective field theory approach for radiative corrections to neutron decay

We develop a new top-down effective field theory approach for radiative corrections to the neutron decay. First, we match the Standard Model to the four-fermion effective field theory. To evaluate radiative corrections at scales of the neutron decay, we perform matching to the heavy-baryon chiral perturbation theory. For the vector coupling constant, we find an agreement with the traditional current-algebra approach at the one-loop level, improve on the resummation of next-to-leading logarithms, and provide an updated extraction of the Vud matrix element.