Leptogenesis in Supersymmetric Standard Model with Right-handed Neutrino *

We show that the leptogenesis is automatic within the supersymmetric standard model if there exist right-handed neutrinos with mass less than Hinf , the expansion rate during the inflation. Its scalar component grows during the inflation due to the quantum fluctuation, oscillates coherently after the inflation, and its decay generates lepton asymmetry. The scenario is naturally embedded into SO(10) GUT without any modifications. We also discuss the case with heavier right-handed neutrino. This work was supported by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Division of High Energy Physics of the U.S. Department of Energy under Contract DE-AC03-76SF00098. On leave of absence from Department of Physics, Tohoku University, Sendai, 980 Japan