Resonant leptogenesis with mild degeneracy

Abstract

Under the assumption of hierarchical right-handed neutrino masses, masses of right-handed neutrinos must be larger than ${10}^{8}\text{ }\text{ }\mathrm{GeV}$ in the standard thermal leptogenesis scenario, while the mass can be reduced to around 5 TeV in a neutrinophilic two Higgs doublet model. On the other hand, resonant leptogenesis can work with the masses of TeV scale. However, necessary degeneracy between the lightest and the second-lightest right-handed neutrino masses means unnatural fine-tuning of the order of ${10}^{9}$. In this paper, we will investigate the resonant leptogenesis scenario in a neutrinophilic two Higgs doublet model. We will find the mass can be reduced to 2 TeV, and the degeneracy becomes much milder as of the order of ${10}^{4}$.