Non-thermal leptogenesis and UV freeze-in of dark matter: impact of inflationary reheating

TL;DR

This paper explores a minimal model where non-thermal leptogenesis and UV freeze-in of dark matter occur simultaneously, with the inflaton influencing their production, and analyzes how different operator dimensions affect the yields and parameter constraints.

Contribution

It introduces a minimal scenario with inflaton coupling to right-handed neutrinos and dark matter via higher-dimensional operators, analyzing their roles in leptogenesis and dark matter production.

Findings

For d=5, inflaton decay into RHNs leads to reheating and DM production from the SM bath.

For d=6, DM is produced directly from RHN scattering, with complex yield evolution.

The model can simultaneously explain baryon asymmetry and dark matter relic density.

Abstract

We study a minimal scenario to realize non-thermal leptogenesis and UV freeze-in of a Standard Model (SM) gauge singlet fermionic dark matter (DM) simultaneously, with inflaton field playing a non-trivial 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 $\Lambda\sim 10^{17}~\rm GeV$ depending on the DM mass. On the other hand, for $d=6$, DM production happens directly from scattering of RHNs (for $\Lambda\gtrsim 10^{14}~\rm GeV$) that results in a very non-trivial evolution of the DM yield. In both these cases, it is possible to explain the observed baryon asymmetry through successful non-thermal 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 non-instantaneous 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.