Double-beta decay and resonances in the nucleus

Abstract

Double-beta decay half-lives are calculated with the assumption that the emission of electron–neutrino pairs occurs via a Δ(1232) resonance in the nucleus. Numerical results are obtained with a quark model for the hadrons. By assuming that total rates are produced by a combination of neutrinoless and two-nuetrino modes, a lepton-nonconservation parameter η ~ 10−5 is obtained. Although the actual modes of decay and underlying mechanisms are undetermined, the present calculation can be used to obtain an upper limit for the probability admixture of resonances in the nucleus of a few percent.