Examination of the consistency of the quasiparticle random-phase approximation approach to double-β decay of 48Ca

The nuclear matrix elements (NMEs) of the neutrinoless and two-neutrino double-beta decays of Ca-48 are calculated by the quasiparticle random-phase approximation (QRPA) with emphasis on the consistency examinations of this calculation method. The main new examination points are the consistency of two ways to treat the intermediate-state energies in the two-neutrino double-beta NME and comparison with the experimental charge-exchange strength functions obtained from Ca-48(p,n) and Ti-48(n,p) reactions. No decisive problem preventing use of the QRPA approach is found. The obtained neutrinoless double-beta NME adjusted by the ratio of the effective and bare axial-vector current couplings is lowest in those calculated by different groups and close to one of the QRPA values obtained by another group.