Shell model progress on neutrinoless double beta decay: nuclear matrix element uncertainties, neutrino exchange mechanism in seesaw models

Abstract

We study the neutrinoless double beta decay in the context of the interacting shell model. Firstly, we estimate the uncertainties associated to the different approximations performed in the calculation of the nuclear matrix elements, which are necessary to obtain information about the neutrino masses. We then study the dependence of the nuclear matrix elements on the mass of the exchanged neutrinos and we discuss, within the type I seesaw model, which will be the contribution to the neutrinoless double beta decay rate of the different extra neutrinos, depending on their mass range. We also discuss how seesaw models could reconcile large rates of neutrinoless double beta decay with stringent cosmological bounds on neutrino masses.