CP-phase effects on the effective neutrino mass mee in the case of quasidegenerate neutrinos

We study the possibility that the three mass states of the ordinary active neutrinos actually split into pairs of quasidegenerate states, with Δmkk'2∼10-12 eV2 or less, as a result of mixing of active neutrinos with sterile neutrinos. While in laboratory experiments these quasidegenerate pairs will look identical to single active states, the CP phase factors associated with active-sterile mixing might cause cancellations in the effective electron neutrino mass mee measured in the neutrinoless double beta decay experiments thereby revealing the split nature of states.