Double-beta decays of light and medium-mass atomic nuclei

Abstract

Most atomic nuclei decay via β decay, a weak interaction process. In second-order β decay, two neutrons decay into two protons, accompanied by the emission of two electrons and two antineutrinos. However, if neutrinos were Majorana particles, this would allow the existence of a hypothetical neutrino-less double-β decay (0νββ), which violates the symmetries of the Standard Model of particle physics because only two electrons are emitted. In this work, we compute the 0νββ decay nuclear matrix elements (NMEs) for light and medium-mass nuclei from 6He to 60Ca. We find larger values of the NMEs for decays where the initial and final nuclei are mirror nuclei. Finally, we find a good correlation between 0νββ NMEs and double Gamow-Teller NMEs, which can be measured in nuclear reactions. This correlation is approximately universal for all decays studied.