Production of massive fermions at preheating and leptogenesis

We present a complete computation of the inflaton decay into very massive f ermions during preheating, including back-reaction effects. We show that he avy fermions are produced very efficiently up to masses of order 10(17)-10( 18) GeV; the accessible mass range is thus even broader than the one for he avy bosons. We apply our findings to the leptogenesis scenario, proposing a new version of it, in which the massive right-handed neutrinos, responsibl e for the generation of the baryon asymmetry, are produced during preheatin g. We also discuss other production mechanisms of right-handed neutrinos in the early Universe, identifying the neutrino mass parameters for which the observed baryon asymmetry is reproduced.