Leptogenesis at Low Scale

A typical problem of the leptogenesis scenario is the mismatch between the maximum reheat temperature implied by gravitino overproduction bound and the minimum temperature required to create thermally the lightest righthanded neutrino. We explore the possibility of baryogenesis via leptogenesis in the presence of low scale mass right-handed neutrino. In such a scenario, righthanded neutrinos are created thermally at low reheat temperatures without relying on non-perturbative production mechanisms. We focus on two specific realizations of the scenario, namely the out-of-equilibrium decay of right-handed neutrinos (Fukugita-Yanagida) and the leptogenesis via the LHu flat direction (Affleck-Dine). We find that in general, the two scenarios are able to produce the required baryon excess for a reasonable amount of CP violation. E-mail: [email protected]