Speaker
Description
The nuclear matrix element of neutrinoless double-β decay is an essential input for determining the neutrino effective mass, if the half-life of this decay is measured. Reliable calculation of this nuclear matrix element has been a long-standing problem because of the diversity of the predicted values of the nuclear matrix element, which depends on the calculation method. In this study, we focus on the shell model and the quasiparticle random-phase approximation. We propose a new method to modify phenomenologically the results of the two methods compensating for the insufficiencies of each method using the information of other methods in a complementary manner. The Gamow-Teller and Fermi components of the nuclear matrix element are considered separately. An extrapolation of the Gamow-Teller component of the shell model is made toward a very large valence single-particle space referring to the running sum of the Gamow-Teller component of the quasiparticle random-phase approximation. We introduce a modification factor to the Gamow-Teller component of the quasiparticle random-phase approximation referring to the charge-change strength function of the shell model in a low-energy region. The Fermi components are modified in a similar manner. The discrepancy of the original components of the two methods is reduced dramatically for Ca-48.
