Relativistic description of nuclear matrix elements in neutrinoless double-beta decay

Abstract

Neutrinoless double-beta decay is related to many fundamental concepts in nuclear and particle physics beyond the Standard Model. We report the first full relativistic description of the nuclear matrix element (NME) governing this process by multi-reference covariant density functional theory (MR-CDFT) based on the point-coupling functional PC-PK1. The dynamic correlations are taken into account by configuration mixing of both particle number and angular momentum projected quadrupole deformed mean-field states for the initial and final nuclei. The NMEs for both the 0_s161 _s13_s178594_s19 0_s161 and 0_s161 _s13_s178594_s19 0_s162 decays in 150Nd are evaluated. The effects of particle number projection, and static and dynamic deformations on the nuclear wave functions, as well as those of the full relativistic structure of the transition operator on the NMEs are studied in detail. The low-energy spectra and electric quadrupole transitions are well reproduced by the full generator coordinate method (GCM) calculation. The resulting NME for the 0_s161 _s13_s178594_s19 0_s161 transition is 5.60, which gives the most optimistic prediction for the next generation of experiments searching for the neutrinoless double beta decay in 150Nd.