Current experimental data allow the zero value for one neutrino mass, either m1 = 0 or m3 = 0. This observation implies that a realistic neutrino mass texture can be established by starting from the limit (a) m1 = m2 = 0 and m3 ≠ 0 or (b) m1 = m2 ≠ 0 and m3 = 0. In both cases, we may introduce a particular perturbation which ensures the resultant neutrino mixing matrix to be the tri-bimaximal mixing pattern or its viable variations. We find that it is natural to incorporate this kind of neutrino mass matrix in the minimal Type-II seesaw model with only one heavy right-handed Majorana neutrino N. We show that it is possible to account for the cosmological baryon number asymmetry in the m3 = 0 case via thermal leptogenesis, in which the CP-violating asymmetry of N decays is attributed to the electron flavor.
Minimal type II seesaw model