Deviation from tri-bimaximal neutrino mixing in A4 flavor symmetry

The tri-bimaximal mixing is a good approximation for the present data of neutrino mixing angles. The deviation from the tri-bimaximal mixing is discussed numerically in the framework of the A4 model. Values of \tan^2\theta_{12}, \sin^2 2\theta_{23} and |U_{e3}| deviate from the tri-bimaximal mixing due to the corrections of the vacuum alignment of flavon fields. It is remarked that \sin^2 2\theta_{23} deviates scarcely from 1 while \sin^2\theta_{12} can deviate from 1/3 considerably and \sin\theta_{13} could be near the present experimental upper bound. The CP violating measure J_{CP} and the effective Majorana neutrino mass m_{ee} are also discussed.Comment: 12 pages, 18 figures, some discussions and references are adde

Seesaw Enhancement of Bi-large Mixing in Two-Zero Textures

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 $m_D$ and right-handed Majorana neutrino mass matrix $M_R$, however, the bi-large mixing is realized via the seesaw mechanism. We present twelve sets of $m_D$ and $M_R$ for the seesaw enhancement and discuss the related phenomena, the $\mu\to e+\gamma$ process and the leptogenesis. The decay rate of $\mu\to e+\gamma$ is enough suppressed due to zeros in the Dirac neutrino mass matrix. Six $m_D$ lead to the lepton asymmetry, which can explain the baryon number in the universe. Other six $m_D$ are the real matrices, which give no CP asymmetry. Modified Dirac neutrino mass matrices are also discussed.Comment: latex file, 16 page

Examining the Geometrical Model with Inverted Mass Hierarchy for Neutrinos

The comprehensive analyses are presented in the model with the inverted mass hierarchy for neutrinos, which follows from a geometrical structure of a (1+5) dimensional space-time where two extra dimensions are compactified on the T^2/Z_3 orbifold. The model gives two large lepton flavor mixings due to the S3 structure in the (1+5) dimensional space-time. It also predicts the lightest neutrino mass as m_3=(1-50)\times 10^{-5}eV and the effective neutrino mass responsible for neutrinoless double beta decays as _{ee}\simeq 50 meV. The low energy CP violation, J_{CP} could be 0.02. On the other hand, the observed baryon asymmetry in the present universe is produced by the non-thermal leptogenesis, which works even at the reheating temperature TR=10^{4}-10^{6}GeV. The correlation between the baryon asymmetry and the low energy CP violation is examined in this model.Comment: 17 pages, 10 figures, a reference is added, minor change in introductio

Embedding the Texture of the Neutrino Mass Matrix into the MaVaNs Scenario

We have embedded the texture of the neutrino mass matrix with three families into the MaVaNs scenario. We take the power-law potential of the acceleron field and a typical texture of active neutrinos, which is derived by the D_4 symmetry and predicts the maximal mixing of the atmospheric neutrino and the vanishing U_{e3}. The effect of couplings among the dark fermion and active neutrinos are studied by putting the current cosmological data and the terrestrial neutrino experimental data. It is found that the neutrino flavor mixings evolve as well as the neutrino masses. Especially, U_{e3} develops into the non-vanishing one and \theta_{atm} deviates from the maximal mixing due to couplings among the dark fermion and active neutrinos.Comment: Sections 3 and 4 are changed and one table is added. 16pages and 2 figure

Prediction of Ue3U_{e3} in Neutrino Mass Matrix with Two Zeros

We have discussed predictions of $|U_{e3}|$ and $J_{CP}$ in the framework of the neutrino mass matrix with two zeros. In the case of the best fit values of $\tan^2\theta_{12}$, $\tan^2\theta_{23}$, $\Delta m^2_{\rm sun}$ and $\Delta m_{\rm atm}^2$, the prediction of $|U_{e3}|$ is $0.11\sim 0.14$. The lower bound of $|U_{e3}|$ is 0.05, which depends on $\tan\theta_{12}$ and $\tan\theta_{23}$. We have investigated the stability of these predictions taking account of small corrections to zeros, which may come from radiative corrections or off-diagonal elements of the charged lepton massmatrix. The lower bound of $|U_{e3}|$ comes down considerably due to the small corrections to zeros.Comment: Figures and discussions are adde