Leptogenesis with sub-electroweak-scale reheating temperature

Abstract

We study the generation of the baryon asymmetry of the Universe via leptogenesis during the post-inflationary reheating epoch, considering reheating temperatures below the temperature of sphaleron freeze-out temperature. Within the framework of a monomial inflaton potential during reheating, we analyze three perturbative reheating scenarios in which the inflaton decays into (i) a pair of SM-like bosons, (ii) a pair of SM-like fermions, or (iii) exclusively into a pair of heavy right-handed neutrinos. For each case, we identify the regions of parameter space that successfully reproduce the observed baryon asymmetry consistently tracking the sphaleron interaction rate during reheating, while satisfying existing cosmological constraints. We also highlight the potential of future primordial gravitational wave observations to probe this class of scenarios.