Isospin corrections for superallowed Fermi β decay in self-consistent relativistic random-phase approximation approaches

Self-consistent random phase approximation (RPA) approaches in the relativistic framework are applied to calculate the isospin symmetry-breaking corrections delta(c) for the 0(+)-> 0(+) superallowed transitions. It is found that the corrections delta(c) are sensitive to the proper treatments of the Coulomb mean field, but not so much to specific effective interactions. With these corrections delta(c), the nucleus-independent Ft values are obtained in combination with the experimental ft values in the most recent survey and the improved radiative corrections. It is found that the constancy of the Ft values is satisfied for all effective interactions employed. Furthermore, the element V-ud and unitarity of the Cabibbo-Kobayashi-Maskawa matrix are discussed. .