Neutrinos: Majorana Mass Limits and Related Issues

ABSTRACT The upper limit on the mass of the Majorana neutrino, extracted from the limits on the non‐observation of the neutrinoless double beta decay, is plugged by uncertainties in the nuclear structure sector, that is the matrix elements of the transition operators which mediate the decay. Recently it was shown that the values of the effective axial‐vector current coupling constant, for the neutrinoless and the two‐neutrino modes of decays, are similar. This striking, and unexpected, result was obtained by extending the nuclear structure sector of the theory, by including vertex corrections and two‐body currents. In this note we shall present and discuss the results obtained for the half‐life of both modes (two‐neutrino and zero neutrino modes) of the double beta decay of Xe, and about the corresponding limits for the mass of the Majorana neutrino.