NEUTRINO OSCILLATION CONSTRAINTS ON NEUTRINOLESS DOUBLE-BETA DECAY

We have studied the constraints imposed by the results of neutrino osc illation experiments on the effective Majorana mass \[m]\ that charact erizes the contribution of Majorana neutrino masses to the matrix elem ent of neutrinoless double-beta decay. We have shown that in a general scheme with three Majorana neutrinos and a hierarchy of neutrino mass es (which corresponds to the standard seesaw mechanism) the results of neutrino oscillation experiments imply rather strong constraints on t he parameter \[m]\ From the results of the first reactor long-baseline experiment CHOOZ and the Bugey experiment it follows that \[m]\less t han or similar to 3X10(-2) eV if Delta m(2) less than or similar to 2 eV(2) (Delta m(2) is the largest mass-squared difference). Hence, we c onclude that the observation of neutrinoless double-beta decay with a probability that corresponds to \[m]\greater than or similar to 10(-1) eV would be a signal for a nonhierarchical neutrino mass spectrum and /or nonstandard mechanisms of lepton number violation.