Neutrino oscillation constraints on neutrinoless double-beta decay

Abstract

We have studied the constraints imposed by the results of neutrino oscillation experiments on the effective Majorana mass $|〈m〉|$ that characterizes the contribution of Majorana neutrino masses to the matrix element of neutrinoless double-beta decay. We have shown that in a general scheme with three Majorana neutrinos and a hierarchy of neutrino masses (which corresponds to the standard seesaw mechanism) the results of neutrino oscillation experiments imply rather strong constraints on the parameter $|〈m〉|.$ From the results of the first reactor long-baseline experiment CHOOZ and the Bugey experiment it follows that $|〈m〉|\ensuremath{\lesssim}3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\mathrm{eV}$ if $\ensuremath{\Delta}{m}^{2}\ensuremath{\lesssim}2{\mathrm{eV}}^{2}$ $(\ensuremath{\Delta}{m}^{2}$ is the largest mass-squared difference). Hence, we conclude that the observation of neutrinoless double-beta decay with a probability that corresponds to $|〈m〉|\ensuremath{\gtrsim}{10}^{\ensuremath{-}1}\mathrm{eV}$ would be a signal for a nonhierarchical neutrino mass spectrum and/or nonstandard mechanisms of lepton number violation.