The minimal Type I seesaw 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 standard model-like Higgs boson and predict TeV-scale scalar states and low- to intermediate-scale hierarchical leptogenesis with ${10}^3\mathrm{GeV}\lesssim M_{N_1}\lesssim {10}^8\mathrm{GeV}$.

• Received 14 June 2015

DOI:https://doi.org/10.1103/PhysRevD.92.033006