Leptogenesis and dark matter from a low scale seesaw mechanism

Abstract

In this paper, we perform a detailed analysis of the phenomenology of leptogenesis and dark matter from a low scale seesaw mechanism. In the framework of Neutrinophilic two Higgs doublet model, we further introduce one scalar singlet $\ensuremath{\phi}$ and one Dirac fermion singlet $\ensuremath{\chi}$, which are charged under a ${Z}_{2}$ symmetry. Assuming the coupling of $\ensuremath{\chi}$ is extremely small, it serves as feebly interacting massive particle (FIMP) dark matter. Heavy right-hand neutrinos $N$ provide a common origin for tiny neutrino mass (via a seesaw mechanism), leptogenesis (via $N\ensuremath{\rightarrow}{\ensuremath{\ell}}_{L}{\mathrm{\ensuremath{\Phi}}}_{\ensuremath{\nu}}^{*}$, ${\overline{\ensuremath{\ell}}}_{L}{\mathrm{\ensuremath{\Phi}}}_{\ensuremath{\nu}}$), and dark matter (via $N\ensuremath{\rightarrow}\ensuremath{\chi}\ensuremath{\phi}$). With hierarchical right-hand neutrino masses, the explicit calculation shows that successful thermal leptogenesis is viable even for TeV-scale ${N}_{1}$ with $0.4\text{ }\text{ }\mathrm{GeV}\ensuremath{\lesssim}{v}_{\ensuremath{\nu}}\ensuremath{\lesssim}1\text{ }\text{ }\mathrm{GeV}$ and lightest neutrino mass ${m}_{1}\ensuremath{\lesssim}{10}^{\ensuremath{-}11}\text{ }\text{ }\mathrm{eV}$. In such a scenario, light FIMP dark matter in the keV to MeV range is naturally expected. The common parameter space for neutrino mass, natural leptogenesis, and FIMP dark matter is also obtained in this paper.