Radiative neutron β-decay in effective field theory

We consider radiative beta-decay of the neutron in heavy baryon chiral perturbation theory, with an extension including explicit Delta degrees of freedom. We compute the photon energy spectrum as well as the photon polarization; both observables are dominated by the electron bremsstrahlung contribution. Nucleon- structure effects not encoded in the weak coupling constants g(A) and g(V) are determined at next-to-leading order in the chiral expansion, and enter at the O(0.5%)-level, making a sensitive test of the Dirac structure of the weak currents possible. (C) 2004 Elsevier B.V. All rights reserved.