Half-life of Xe 136 for neutrinoless double- β decay calculated with effective axial-vector current coupling unified for two-neutrino and neutrinoless double- β decay modes

Abstract

The upper limit on the mass of the Majorana neutrino, extracted from the limits on the nonobservation ofthe neutrinoless double-β (0νββ) decay, is hampered by uncertainties in the matrix elements of the transitionoperators. Recently, we have shown that the values of the effective axial-vector current coupling constants (g effA )for the 0νββ and the two-neutrino double-β decays are close. This striking result was obtained for the first timeby including vertex corrections and two-body currents in these matrix elements. In this Letter, we calculate the0ν) of 136 Xe using this closeness and show the convergence of the half-life withhalf-life for the 0νββ decay (T 1/2effrespect to the variation of the method to determine g effA . The closeness of the g A of the two decay modes plays0νeffa decisive role in predicting T 1/2 . The appropriate value of g A depends on the assumptions made for the sectorsof the nuclear structure and transition operators of the calculations within the perturbation scheme. The value∗g effA ≈ 1 is obtained when the SkM is used to describe the nuclear structure component, while a smaller value ofeffg A is obtained by applying a less realistic interaction like the SGII one.