Nonthermal leptogenesis and UV freeze-in of dark matter: Impact of inflationary reheating.

We study a minimal scenario to realize nonthermal leptogenesis and UV freeze-in of a Standard Model (SM) gauge singlet fermionic dark matter (DM) simultaneously, with inflaton field playing a nontrivial role in their yields. The renormalizable interactions are restricted to the SM fields, two right-handed neutrinos (RHN) and inflaton coupling exclusively to the RHNs, while the DM couples to both the SM and the RHNs only via operators of dimension d>4. Considering two separate cases of d={5,6}, we show that for d=5, inflaton decay into RHNs followed by their subsequent decay into SM particles lead to both reheating as well as DM production from the SM bath. This requires a cut off scale as large as Λ∼1017  GeV depending on the DM mass. On the other hand, for d=6, DM production happens directly from scattering of RHNs (for Λ≳1014  GeV) that results in a very nontrivial evolution of the DM yield. In both these cases, it is possible to explain the observed baryon asymmetry through successful nonthermal leptogenesis via the decay of the RHNs, together with the Planck observed relic density of the DM via pure UV freeze-in mechanism. Taking into account both instantaneous as well as noninstantaneous reheating separately, we constrain the parameter space of this minimal scenario from relevant phenomenological requirements including sub-eV scale active neutrino masses and their mixing. [ABSTRACT FROM AUTHOR]