Neutrinoless ??-decay nuclear matrix elements from two-neutrino ??-decay data

We study two-neutrino (2v beta beta) and neutrinoless double-beta (0v beta beta) decays in the nuclear shell model and proton-neutron quasiparticle random-phase approximation (pnQRPA) frameworks. Calculating the decay half-life of several dozens of nuclei ranging from calcium to xenon with the shell model, and of beta beta emitters with a wide range of proton-neutron pairing strengths in the pnQRPA, we observe good linear correlations between 2v beta beta- and 0v beta beta-decay nuclear matrix elements for both methods. We then combine the correlations with measured 2v beta beta-decay half-lives to predict 0v beta beta-decay matrix elements with theoretical uncertainties based on our systematic calculations. Our results include two-body currents and the short-range 0v beta beta-decay operator.