2-NEUTRINO DOUBLE BETA-DECAY OF CA-48

We have performed quasiparticle random phase approximation (QRPA) calculations for the 2nubetabeta decay matrix element M(GT)2nu of Ca-48 using realistic effective interactions derived from the Paris, Bonn, and Reid potentials. Unlike earlier QRPA calculations where the BCS self-energies were suppressed, we have retained these self-energies together with the use of the single-particle levels provided by a Ca-40 core. Different choices for the single-particle levels are employed, and their effects on M(GT)2nu are compared. A majority of our calculated M(GT)2nu matrix elements are in good agreement with the experimental bounds of \M(GT)2nu\ < 0.05 MeV-1, and exhibit good stability with respect to the variation of the particle-particle interaction strength g(pp).