Neutrino masses, mixing and leptogenesis in a two Higgs doublet model “for the third generation”

We examine neutrino oscillations in a two Higgs doublet model (2HDM) in which the second doublet couples only to the third generation right-handed up-fermions, i.e., to tR and to N3 which is the heaviest right-handed Majorana neutrino. The inherently large tanβ of this model can naturally account for the large top mass and, based on a quark-lepton similarity ansatz, when embedded into a see-saw mechanism it can also account for the observed neutrino masses and mixing angles giving a very small θ13: −0.017≲θ13≲0.021 at 99% CL, and a very restrictive prediction for the atmospheric mixing angle: 42.9°≲θatm≲45.2° at 99% CL. The large value of tanβ also sets the mass scale of the heaviest right-handed Majorana neutrino N3 and triggers successful leptogenesis through a CP-asymmetry in the decays of the N1 (lightest right-handed Majorana) which is tan2β enhanced compared to the CP-asymmetry obtained in models for leptogenesis with one Higgs doublet or in the MSSM. This enhancement allows us to relax the lower bound on MN1 and consequently also the lower bound on the reheating temperature of the early universe.