Study of production mechanism of universe's baryon number and neutrino masses

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The seesaw mechanism that explains naturally the observed small neutrino masses predicts heavy Majorana neutrinos. It is known that the decay of the heavy Majorana neutrinos produce lepton asymmetry which is converted to the baryon asymmetry. Thus, one may explain the baryon-number asymmetry in the universe by the decay of the Majorana neutrino decay. In the present project we have shown that it is indeed the case and that the observed neutrino masses are very consistent with the mechanism of the above baryogenesis. In particular, we have considered inflation models based on supergravity and found that most of the inflation models produce too much gravitinos if the above baryogenesis takes place. We have also found that gauge and anomaly mediation scenarios for supersymmetry breaking do not suffer from this problem. Therefore the present baryogenesis scenario based on the decay of heavy Majorana neutrinos predicts certain spectra of super-particles at low energies, which will be tested at the near future collider experiments such as LHC.