Isoscalar pairing interaction for the quasiparticle random-phase approximation approach to double-β and β decays

AbstraktAbstract

We have proposed in a series of previous articles a method to determine the effective axial-vector current coupling and the strength of the isoscalar proton-neutron pairing interaction for calculating the nuclear matrix elements of the neutrinoless double-β (0νββ) decay by the quasiparticle random-phase approximation (QRPA). The combination of these two parameters has had an uncertainty in the QRPA approach, but now this uncertainty is removed by introducing a mathematical identity derived under the closure approximation to the nuclear matrix element of the 0νββ decay. In this article, we apply our method to the 0νββ decays of 136Xe and 130Te and show the nuclear matrix elements and reduced half-lives. Our calculation is tested first by a self-check method using the two-neutrino double-β decay, and this test ensures the application of our method to 136Xe. It turns out, however, that our method is not successful in 130Te. Further tests are made for our calculation, and satisfactory results are obtained for 136Xe.

We have proposed in a series of previous articles a method to determine the effective axial-vector current coupling and the strength of the isoscalar proton-neutron pairing interaction for calculating the nuclear matrix elements of the neutrinoless double-β (0νββ) decay by the quasiparticle random-phase approximation (QRPA). The combination of these two parameters has had an uncertainty in the QRPA approach, but now this uncertainty is removed by introducing a mathematical identity derived under the closure approximation to the nuclear matrix element of the 0νββ decay. In this article, we apply our method to the 0νββ decays of 136Xe and 130Te and show the nuclear matrix elements and reduced half-lives. Our calculation is tested first by a self-check method using the two-neutrino double-β decay, and this test ensures the application of our method to 136Xe. It turns out, however, that our method is not successful in 130Te. Further tests are made for our calculation, and satisfactory results are obtained for 136Xe.