  Observed baryon asymmetry can be achieved not only by the decay of
right-handed neutrinos but also by the scattering processes in the reheating
era. In the latter scenario, new physics in high energy scale does not need to
be specified, but only two types of the higher dimensional operator of the
standard model particles are assumed in the previous work. In this paper, we
examine the origin of the higher dimensional operators assuming models with a
certain seesaw mechanism at the high energy scale. The seesaw mechanism seems
to be a simple realization of the reheating era leptogenesis because the lepton
number violating interaction is included. We show that the effective
interaction giving CP violating phases is provided in the several types of
models and also the reheating era leptogenesis actually works in such models.
Additionally, we discuss a possibility for lowering the reheating temperature
in the radiative seesaw models, where the large Yukawa coupling is naturally
realized.
