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

AbstraktAbstract

The upper limit on the mass of the Majorana neutrino, extracted from the limits on the nonobservation of the neutrinoless double-β (0νββ) decay, is hampered by uncertainties in the matrix elements of the transition operators. Recently, we have shown that the values of the effective axial-vector current coupling constants (geffA) for the 0νββ and the two-neutrino double-β decays are close. This striking result was obtained for the first time by including vertex corrections and two-body currents in these matrix elements. In this Letter, we calculate the half-life for the 0νββ decay (T^0ν_1/2) of 136Xe using this closeness and show the convergence of the half-life with respect to the variation of the method to determine geffA . The closeness of the geffA of the two decay modes plays a decisive role in predicting T^0ν_1/2. The appropriate value of geffA depends on the assumptions made for the sectors of the nuclear structure and transition operators of the calculations within the perturbation scheme. The value geffA ≈ 1 is obtained when the SkM∗ is used to describe the nuclear structure component, while a smaller value of geffA is obtained by applying a less realistic interaction like the SGII one.

The upper limit on the mass of the Majorana neutrino, extracted from the limits on the nonobservation of the neutrinoless double-β (0νββ) decay, is hampered by uncertainties in the matrix elements of the transition operators. Recently, we have shown that the values of the effective axial-vector current coupling constants (geffA) for the 0νββ and the two-neutrino double-β decays are close. This striking result was obtained for the first time by including vertex corrections and two-body currents in these matrix elements. In this Letter, we calculate the half-life for the 0νββ decay (T^0ν_1/2) of 136Xe using this closeness and show the convergence of the half-life with respect to the variation of the method to determine geffA . The closeness of the geffA of the two decay modes plays a decisive role in predicting T^0ν_1/2. The appropriate value of geffA depends on the assumptions made for the sectors of the nuclear structure and transition operators of the calculations within the perturbation scheme. The value geffA ≈ 1 is obtained when the SkM∗ is used to describe the nuclear structure component, while a smaller value of geffA is obtained by applying a less realistic interaction like the SGII one.