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

Abstract

Nuclear matrix elements (NMEs) for two-neutrino double-beta decay ($2\nu \beta \beta$) are studied in the framework of relativistic nuclear energy density functional (REDF). 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 relativistic energy density functional (REDF-QRPA). Three effective interactions have been 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: ${}^{48}$Ca, ${}^{76}$Ge, ${}^{82}$Se, ${}^{96}$Zr, ${}^{100}$Mo, ${}^{116}$Cd, ${}^{124}$Xe, ${}^{128}$Te, ${}^{130}$Te, ${}^{136}$Xe and ${}^{150}$Nd. 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.

Comments: 18 pages, 12 figures, accepted for publication in Physical Review C