Speaker
Description
We calculate the nuclear matrix elements of the neutrinoless and the two-neutrino double-β decays for 136Xe to 136Ba with the higher-order corrections for the transition operators in terms of perturbation interaction. This is a study of the effects that cannot be included in the initial and the final nuclear wave functions. The new terms are derived by an extension of the usual leading-order calculation using the perturbation theory. We use the lowest-order corrections of the vertex correction and the two-body current. It turned out that the absolute values of these correction terms are comparable with that of the leading term. The effective axial-vector current coupling for the two-neutrino double-β decay with the new nuclear matrix element to reproduce the experimental half-life is significantly larger than that of the leading-order calculation and closer to the bare value for nucleons in the vacuum. We obtain the effective axial-vector current couplings using the leading-order components to reproduce the perturbed nuclear matrix elements with the bare coupling. Those effective couplings for the neutrinoless and the two-neutrino decays are not significantly different. This is the new important finding.
