Natural leptogenesis and neutrino masses with two Higgs doublets

Abstract

The minimal Type I see-saw model cannot explain the observed neutrino masses and the baryon asymmetry of the Universe via hierarchical thermal leptogenesis without ceding naturalness. We show that this conclusion can be avoided by adding a second Higgs doublet with $\tan \beta \gtrsim 4$. The models considered naturally accommodate a SM-like Higgs boson, and predict TeV-scale scalar states and low- to intermediate-scale hierarchical leptogenesis with $10^3\text{ GeV}\lesssim M_{N_1}\lesssim 10^8\text{ GeV}$.

Comments: 12 pages, 6 figures, v2 minor changes plus updated references