Low-scale Fermion Triplet Leptogenesis

In this paper we consider the possibility of generating the observed baryon asymmetry of the Universe via leptogenesis in the context of triplet fermion mediated type-III seesaw model of neutrino mass. With a hierarchical spectrum of the additional fermions, the lower bound on the lightest triplet mass is $\sim 10^{10} {\rm~GeV}$ for successful leptogenesis, a couple of orders higher than that of type-I case. We investigate the possibility of lowering this bound in the framework of two Higgs doublet models. We find that the bounds can be lowered upto $10^7$ GeV for a hierarchical spectrum. If we include the flavor effects then a further lowering by one order of magnitude is possible. We also discuss if such lowering can be compatible with the naturalness bounds on the triplet mass.