Effects of perturbation for transition operator of double-${\beta}$ decay on nuclear matrix element, effective axial-vector current coupling, and half-life

Abstract

We calculate the nuclear matrix element (NME), effective axial-vector current coupling $g_A^\mathrm{eff}$, and half-life of the double-$\beta$ ($\beta\beta$) decay using the transition operator perturbed by the nuclear interaction. The correction terms for the NME are obtained by extending the hadron sector to a higher order in terms of the Rayleigh-Schr\"{o}dinger perturbation theory. The NME calculations are performed for the neutrinoless $\beta\beta$ ($0\nu\beta\beta$) and the two-neutrino $\beta\beta$ ($2\nu\beta\beta$) decays of $^{136}$Xe. The nuclear wave functions are calculated by the quasiparticle random-phase approximation (QRPA) with the Skyrme, the Coulomb, and the contact pairing interactions. Sufficiently large single-particle valence spaces are used. The correction terms for the NME are comparable with the leading term in absolute value, and the sum of the corrections has the opposite sign to that of the leading term. The $g_A^\mathrm{eff}$'s for the $\beta\beta$ NME are calculated by a few methods depending on the truncation of the NME and the half-life referred to. Similarities are found between some of these $g_A^\mathrm{eff}$'s including those of the $0\nu\beta\beta$ NME. This leads to the conclusion that the value of $g_A^\mathrm{eff}$ can indeed be determined by the perturbed transition operator. It is in a comparable range of the $g_A$ for the $2\nu\beta\beta$ NME. The perturbation effect on the $2\nu\beta\beta$ half-life is discussed by comparing the calculated half-lives with the different $g_A$'s and the NME components.