Morimitsu Tanimoto

Atmospheric neutrino oscillation and a phenomenological lepton mass matrix

We propose simple phenomenological lepton mass matrices which describe the three neutrinos almost degenerate in mass, leading to a very large mixing angle between

CP violation in neutrino oscillation and leptogenesis

\nu_\mu

Zee mass matrix and bi-maximal neutrino mixing

and

CP violation in bilarge lepton mixing

\nu_\tau

Large mixing angle MSW solution in U(1) flavor symmetry

, as consistent with a recent report on atmospheric neutrino oscillation from the Superkamiokande collaboration. Our matrix model also gives

Renormalization effect on large neutrino flavor mixing in the minimal supersymmetric standard model

\nu_e-\nu_\mu

Democratic mass matrices from broken O(3)L×O(3)R flavor symmetry

mixing in agreement with the value required for neutrino oscillation to explain the solar neutrino problem.

Vacuum neutrino oscillations of solar neutrinos and lepton mass matrices

We study the correlation between CP violation in neutrino oscillations and leptogenesis in the framework with two heavy Majorana neutrinos and three light neutrinos. Among three unremovable CP phases, a heavy Majorana phase contributes to leptogenesis. We show how the heavy Majorana phase contributes to Jarlskog determinant J as well as neutrinoless double beta decay by identifying a low energy CP-violating phase which signals the CP-violating phase for leptogenesis. For some specific cases of the Dirac mass term of neutrinos, a direct relation between lepton number asymmetry and J is obtained. We also study the effect coming from the phases which are not related to leptogenesis.

Neutrino mass matrix with two zeros and leptogenesis

Abstract We investigate neutrino masses and mixings within the framework of the Zee mass matrix, with three lepton flavors. It is shown that the bi-maximal solution is the only possibility to reconcile atmospheric and solar neutrino data, within this ansatz. We obtain two almost degenerate neutrinos, which are mixtures of all three neutrino flavors, with heavy masses ≃ Δ m atm 2 . The predicted mass of the lightest neutrino, which should consist mostly of νμ and ντ, is ≃ Δ m ⊙ 2 /(2 Δ m atm 2 ) .

Explicit CP Violation of the Higgs Sector in the Next-to-Minimal Supersymmetric Standard Model

We propose a scheme of lepton mixing in which the unitary matrix that diagonalizes the neutrino mass matrix is bimaximal and the deviation from the bimaximal of the lepton mixing matrix is due to the unitary matrix that diagonalizes the charged-lepton mass matrix. This matrix is assumed to be hierarchical, like the quark mixing matrix. It is shown that in general it is possible to have a sizable value for