Two-neutrino double-beta decay matrix elements for ground and excited states of 76Ge and 82Se nuclei

Here we present the theoretical results for the Gamow-Teller two-neutrino double-beta decay (DBD) matrix elements for 01+→01+ and 21+ transitions in the case of 76Ge to 76Se and 82Se to 82Kr nuclei. The calculations have been done in the framework of the variation after projection on the Hartree-Fock-Bogoliubov model with 2p1/2, 2p3/2, 1f5/2, and 1g9/2 valence space employing the modified Kuo-Brown interactions. The value of DBD half-lives result in excellent agreement for ground state (g.s.) to g.s. excitations of 76Ge and 82Se nuclei. Our results are in contrast with existing theoretical calculations for g.s. to 2+ excited state and are much closer to the experimental limits