Amarjit Soni

Massive neutrinos in a grounds-up approach

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 t{sub R} and N{sub 3} which is the heaviest right-handed Majorana neutrino. The inherently large tan {beta} of this model can naturally account for the large top-quark mass and, based on a quark-lepton similarity ansatz, when embedded into a seesaw mechanism it can also account for the observed neutrino masses and mixing angles giving a very small {theta}{sub 13}: -0.96{sup 0} {approx}< {theta}{sub 13} {approx}< 1.36{sup 0} at 99% CL, and a very restrictive prediction for the atmospheric mixing angle: 42.9{sup 0} {approx}< {theta}{sub atm} {approx}< 45.2{sup 0} at 99% CL. The large value of tan {beta} also sets the mass scale of the heaviest right-handed Majorana neutrino N{sub 3} and triggers successful leptogenesis.