Neutrino mixing and leptogenesis in the type II seesaw mechanism

Abstract

In the framework of the type II seesaw mechanism we propose two simple but instructive ansatze for neutrino mixing and leptogenesis. In each ansatz, the effective Majorana neutrino mass matrix is composed of two parts-the part with Z(2) symmetry arises from the ordinary type I seesaw mechanism and the part with S-3 symmetry arises from an additional Higgs triplet vacuum expectation value. The two ansatze can simultaneously account for the current neutrino oscillation data and the cosmological baryon number asymmetry via leptogenesis.