CP-phase effects on the effective neutrino massmeein the case of quasidegenerate neutrinos

Abstract

We study the possibility that the three mass states of the ordinary active neutrinos actually split into pairs of quasi-degenerate states, with $\Delta m^2_{kk'} \sim 10^{-12}$ eV$^2$ or less, as a result of mixing of active neutrinos with sterile neutrinos. Although these quasi-degenerate pairs will look in laboratory experiment identical to single active states, the CP phase factors associated with active-sterile mixing might cause cancellations in the effective electron neutrino mass $m_{ee}$ measured in the neutrinoless double beta decay experiments thereby revealing the split nature of states.