Nuclear matrix elements for Majoron emitting double-$\beta$ decay

Abstract

A complete calculation of the nuclear matrix elements (NME) for Majoron emitting neutrinoless double beta decay within the framework of IBM-2 for spectral indices $n=1,3,7$ is presented. By combining the results of this calculation with previously calculated phase space factors (PSF) we give predictions for expected half-lives. By comparing with experimental limits on the half-lives we set limits on the coupling constants $⟨g_{ee}^M⟩$ of all proposed Majoron-emitting models.