%0 Journal Article %T Quenching of spin operators in the calculation of radiative corrections for nuclear beta decay %A I. S. Towner %J Physics %D 1994 %I arXiv %R 10.1016/0370-2693(94)91000-6 %X Calculations of the axial-vector component to the radiative correction for superallowed Fermi $0^+ \rightarrow 0^+$ nuclear beta decay are here modified with quenched rather than free-nucleon coupling constants for the axial-vector and electromagnetic interactions with nucleons. The result increases the deduced value of $V_{ud}$ but does not restore unitarity in the CKM matrix. %U http://arxiv.org/abs/nucl-th/9405031v1