The SNO solar neutrino data, neutrinoless double-beta decay and neutrino mass spectrum.

Abstract

Assuming 3-nu mixing and massive Majorana neutrinos, we analyze the implications of the results of the solar neutrino experiments, including the latest SNO data, which favor the LMA MSW solution of the solar neutrino problem with tan(2) thetacircle dot < 1, for the predictions of the effective Majorana mass I (m) I in neutrinoless double beta-decay. Neutrino mass spectra with normal mass hierarchy, with inverted hierarchy and of quasi-degenerate type are considered. For cos 2thetacircle dotgreater than or similar to 0.26, which follows (at 99.73% C.L.) from the SNO analysis of the solar neutrino data, we find significant lower limits on I (m) I in the cases of quasi-degenerate and inverted hierarchy neutrino mass spectrum, \<m>\ greater than or similar to 0.035 eV and \<m>\ greater than or similar to 8.5 x 10(-3) eV, respectively. If the spectrum is hierarchical the upper limit holds \<m>\ greater than or similar to 8.2 x 10(-3) eV. Correspondingly, not only a measured value of \<m>\ not equal 0, but even an experimental upper limit on I (m) I of the order of few x 10(-2) eV can provide information on the type of the neutrino mass spectrum; it can provide also a significant upper limit on the mass of the lightest neutrino m(1).