Two-neutrino double-β decay matrix elements based on a relativistic nuclear energy density functional

Nuclear matrix elements (NMEs) for two-neutrino double-P decay (2vPP) are studied in the framework of a relativistic nuclear energy density functional. The properties of nuclei involved in the decay are obtained using the relativistic Hartree-Bardeen-Cooper-Schrieffer theory and relevant nuclear transitions are described using the relativistic proton-neutron quasiparticle random phase approximation based on the relativistic energy density functional. Three effective interactions are employed, including density-dependent meson-exchange (DD-ME2) and point-coupling interactions (DD-PC1 and DD-PCX), and pairing correlations are described consistently both in T = 1 and T = 0 channels using a separable pairing interaction. The optimal values of T = 0 pairing strength parameter V-0pp are constrained by the experimental data on beta-decay half-lives. The 2 nu beta beta matrix elements and half-lives are calculated for several nuclides experimentally known to undergo this kind of decay:Ca-48, Ge-76, Se-82, Zr-96, Mo-100, Cd-116, Xe-124, Te-128, Te-130, Xe-136, and Nd-150. The model dependence of the NMEs and their sensitivity on V-0pp is investigated, and the NMEs obtained using optimal values of V-0pp are discussed in comparison to previous studies. The results of the present work represent an important benchmark for the future applications of the relativistic framework in studies of neutrinoless double-beta decay.