Reliability of QRPA approach to ββ and β decays

We investigate the reliability of the quasiparticle random-phase approximation (QRPA) in application to the nuclear matrix element (NME) of the double-β decay of 136Xe. We examine the dependence of the NME of the two-neutrino double-β (2νββ) decay on the choice of the set of the intermediate-state energies, spectrum of the intermediate nucleus, the Gamow-Teller (GT) strength distribution, the GT strengths of the β decays of a nearby nucleus, and a higher-order term of the 2νββ NME recently proposed. The QRPA approach is a good approximation to the decay instance of 136Xe → 136Ba.We investigate the reliability of the quasiparticle random-phase approximation (QRPA) in application to the nuclear matrix element (NME) of the double-β decay of 136Xe. We examine the dependence of the NME of the two-neutrino double-β (2νββ) decay on the choice of the set of the intermediate-state energies, spectrum of the intermediate nucleus, the Gamow-Teller (GT) strength distribution, the GT strengths of the β decays of a nearby nucleus, and a higher-order term of the 2νββ NME recently proposed. The QRPA approach is a good approximation to the decay instance of 136Xe → 136Ba.