Seesaw enhancement of bi-large mixing in two-zero textures

Abstract

The seesaw enhancement of the bi-large mixings are discussed for the two-zero textures of the neutrino mass matrix. There are no large mixings in both Dirac neutrino mass matrix mD and right-handed Majorana neutrino mass matrix MR, however, the bi-large mixing is realized via the seesaw mechanism. We present twelve sets of mD and MR for the seesaw enhancement and discuss the related phenomena, the μ→e+γ process and the leptogenesis. The decay rate of μ→e+γ is enough suppressed due to zeros in the Dirac neutrino mass matrix. Six mD lead to the lepton asymmetry, which can explain the baryon number in the universe. Other six mD are the real matrices, which give no CP asymmetry. Modified Dirac neutrino mass matrices are also discussed.