The neutrinoless double β decay and the neutrino mass hierarchy

Recently the evidence of the neutrinoless double beta (Ovbetabeta) decay has been announced. This means that neutrinos are Majorana particles and their mass hierarchy is forced to certain patterns in the diagonal basis of charged lepton mass matrix. We estimate the magnitude of Ovbetabeta decay in the classification of the neutrino mass hierarchy patterns as Type A, m(1,2) much less than m(3), Type B, m(1) similar to m(2) much greater than m(3), and Type C, m(1) similar to m(2) similar to m(3), where m(i) is the ith generation neutrino absolute mass. The data of Ovbetabeta decay experiment suggest that the neutrino mass hierarchy pattern should be Type B or C. Type B predicts a small magnitude of Ovbetabeta decay which is just edge of the allowed region of experimental value in 95% c.l., where Majorana CP phases should be in a certain parameter region. Type C can induce the suitably large amount of Ovbetabeta decay which is consistent with the experimental data, where overall scale of degenerate neutrino mass plays a crucial role, and its large value can induce the large Ovbetabeta decay in any parameter regions of Majorana CP phases.