概要:
Flavor symmetry has been discussed as one approach to explain the flavor structure. In particular, non-Abelian discrete symmetries, which naturally explains the neutrino mixing pattern, have been studied. Recently, it has been proposed that the modular symmetry due to the compactification of extra dimensions can be the origin of these non-Abelian discrete symmetries, and these discrete symmetries originating from the modular symmetry has been discussed. In this talk, we consider a model with A_4 symmetry proposed and analyzed by Kobayashi, Omoto, Shimizu, Takagi, Tanimoto, and Tatsuishi. In this model, neutrino masses and lepton mixing angles from neutrino oscillation experiments are well explained, and characteristic patterns of CP violation are predicted. In order to explain the baryon asymmetry of the universe, we discuss the leptogenesis in this model. In particular, we show the correlation between the produced baryon number and the Dirac CP phase and/or Majorana CP phases. Furthermore, we present right-handed neutrino masses which can explain the observed value of the baryon asymmetry of the universe, are only present in a limited range.
