Mixing and CP violation with Quasidegenerate Majorana Neutrinos

We study the exactly degenerate case for three lefthanded Majorana neutrinos building a general parametrization for the leptonic mixing matrix characterized by two angles and one CP violating phase and identify a weak-basis invariant relevant, in this case, for CP violation. After lifting the degeneracy, this parametrization accommodates the present data on atmospheric and solar neutrinos, as well as neutrinoless double beta decay. Some of the leptonic mixing ansätze suggested in the literature correspond to special cases of this parametrization. To appear in “Particle Physics on the Boundary of the Millenium”, Proceedings of the 9th Lomonosov Conference on Elementary Particle Physics, ed. by Alexander Studenikin published by Interregional Centre for Advanced Studies, Moscow, Russia, 2000 e-mail: [email protected] 2 On sabbatical leave, visiting SLAC Stanford Linear Accelerator Center, partially supported by Department of Energy, contract DE-AC03-76SF00515, FLAD Fundação Luso Americana para o Desenvolvimento and GTAE Grupo Teórico de Altas Energias. E-mail:[email protected], [email protected] e-mail: [email protected]