Fermion dark matter with N2 leptogenesis in minimal scotogenic model

Abstract

We study the possibility of singlet fermion dark matter (DM) and successful leptogenesis in minimal scotogenic model which also provides a common origin of DM and light neutrino masses. In this scenario, where the standard model (SM) is extended by three gauge singlet fermions and one additional scalar doublet, all odd under an in-built Z2 symmetry, the lightest singlet fermion which also happens to be the lightest Z2 odd particle, can be either thermal or non-thermal DM candidate depending upon the strength of its couplings with SM leptons and the Z2 odd scalar doublet. In both the scenarios, the Z2 odd scalar doublet plays a non-trivial role either by assisting coannihilation with thermal DM or by providing a source for non-thermal DM via decay. The heavier Z2 odd singlet fermion produces a net lepton asymmetry through its out-of-equilibrium decay into SM leptons and Z2 odd scalar doublet. We show that the requirement of producing the observed baryon asymmetry pushes the scale of leptogenesis in case of normal ordering of light neutrino masses to several order of magnitudes above TeV scale. In case of inverted ordering however, it is possible to have successful N2 leptogenesis at a scale of few tens of TeV . Inclusion of lepton flavour effects lowers this scale of leptogenesis by around an order of magnitude in both the cases. Correct DM abundance can be realised either by thermal freeze-out or by freeze-in mechanism in different parts of the parameter space that can have interesting prospects for ongoing experiments.