T-odd momentum correlation in radiative β decay

We consider neutron radiative beta decay, n -> pe(-)(nu) over bar (e)gamma, and compute the T-odd momentum correlation in the decay rate characterized by the kinematical variable xi = I-v . (I-e x k) arising from electromagnetic final-state interactions in the standard model. Our expression for the corresponding T-odd asymmetry A(xi)(SM) is exact in O(alpha) up to terms of recoil order, and we evaluate it numerically under various kinematic conditions. Noting the universality of the V-A law in the absence of recoil-order terms, we retain the parametric dependence on masses and coupling constants throughout, so that our results serve as a template for the computation of A(xi)(SM) in allowed nuclear radiative beta decays and hyperon radiative beta decays as well.