Extracting information on the [formula omitted] decays from the [formula omitted] decays

Abstract

We have analyzed the relation between the two-neutrino ( 2 ν β β ) and neutrinoless ( 0 ν β β ) double beta decays of 76Ge, 82Se, 100Mo, and 116Cd. The relevant nuclear matrix elements have been calculated by using the proton–neutron quasiparticle random-phase approximation (pn-QRPA) with realistic two-body interactions. The dependence of the calculated matrix elements on the strength g pp of the particle–particle part of the proton–neutron two-body interaction is investigated. Recently a procedure was proposed where data on 2 ν β β -decay half-lives could be used to derive appropriate values of g pp for calculating the 0 ν β β -decay matrix elements. Following this procedure, we have determined the allowed values of g pp by including experimental errors of the measured 2 ν β β -decay half-lives and the uncertainties in the axial-vector coupling constant g A . This set of g pp values is used to predict single-beta and 0 ν β β observables. Careful study of these observables points to serious shortcomings in the adopted procedure.