Bi-maximal Neutrino Mixing Pattern Reexamined

The compelling experimental evidences for oscillations of solar, atmospheric and reactor neutrinos imply the existence of 3-neutrino mixing in vacuum. We review the phenomenology of 3-neutrino mixing, and the current data on the 3-neutrino mixing parameters. The opened questions and the main goals of future research in the field of neutrino mixing and oscillations are outlined. A phenomenological approach for understanding the pattern of neutrino mixing as an interplay betwee...

The PMNS neutrino mixing matrix U_{PMNS} is in general a product of two unitary matrices U_{lep} and U_{\nu} arising from the diagonalization of the charged lepton and neutrino mass matrices, U_{PMNS} = U^{\dagger}_{lep} U_{\nu}. Assuming that U_{\nu} is a bimaximal mixing matrix, we investigate the possible forms of U_{lep}. We identify three possible generic structures of U_{lep}, which are compatible with the existing data on neutrino mixing. One corresponds to a hierarchi...

We discuss models of neutrino masses that lead to a large mixing angle for atmospheric neutrino oscillations. In particular we study a mechanism where a simple texture for the Dirac matrix leads to the observed pattern of mixings for a continuous range of Majorana matrices in a reasonably natural way. Both nearly maximal and small mixing solutions for solar neutrinos are compatible with this model. Possible dynamical realizations are discussed and a detailed example in terms ...

We demonstrate that an $SU(2)_L\times U(1)_Y$ model with extended Higgs sector gives rise to bi-maximal neutrino mixing through the incorporation of SO(3) flavour symmetry and discrete symmetry. The neutrino and the charged lepton masses are generated due to higher dimensional terms. The hierarchical structures of neutrinos and charged leptons are obtained due to inclusion of SO(3) flavour symmetry and discrete symmetry.The model can accommodate the vacuum oscillation solutio...

We take up the point of view that Yukawa couplings can be either 0 or 1, and the mass patterns of fermions are generated purely from the structure of the Yukawa matrices. We utilize such neutrino as well as charged leptonic textures which lead to (maximal) mixing angles of $\pi/4$ in each sector for relevant transitions. The combined leptonic CKM mixing angles are $\pi/4 \pm \pi/4$ which lead to very small $\sin^2 2 \Theta$ relevant to solar neutrino and LSND experiments. We ...

We propose a generalized version of the Tri-Bi-Maximal (TBM) ansatz for lepton mixing, leading to non-zero reactor angle $\theta_{13}$ and CP violation. The latter is characterized by two CP phases. The Dirac phase affecting neutrino oscillations is nearly maximal ($\delta_{CP} \sim \pm \pi/2$), while the Majorana phase implies narrow allowed ranges for the neutrinoless double beta decay amplitude. The solar angle $\theta_{12}$ lies nearly at its TBM value, while the atmosphe...

In a model with four neutrino mass eigenstates grouping in two narrow doublets the condition of maximal mixing of the doublet neutrino components leads to a simple four-neutrino mixing matrix which is related to two connected effective two-neutrino mixing patterns. As a result, large values of the neutrino oscillation amplitudes for both the solar and atmospheric neutrino anomalies appear quite naturally if the LSND data are accepted.

We present simple and predictive scenarios for neutrino masses which lead to a bimaximal pattern of mixings that apparently provides the best fit to the current solar and atmospheric neutrino data. It is shown that an approximate global L_e-L_\mu-L_\tau symmetry, broken only by Planck scale effects, can naturally explain the bimaximal mixing pattern. In one scenario, the solar neutrino oscillation parameters are induced entirely through radiative renormalization group effects...

We discuss neutrino masses in the framework of a minimal extension of the minimal supersymmetric standard model (MSSM) consisting of an additional single right-handed neutrino superfield $N$ with a heavy Majorana mass $M$, which induces a single light see-saw mass $m_{\nu_3}$ leaving two neutrinos massless at tree-level. This trivial extension to the MSSM may account for the atomospheric neutrino data via $\nu_{\mu}\to \nu_{\tau}$ oscillations by assuming a near maximal mixin...

Current solar and atmospheric neutrino oscillation data seem to favor a bimaximal pattern for neutrino mixings where the matrix elements U_{e2} and U_{\mu 3} are of order one, while U_{e3} is much smaller. We show that such a pattern can be obtained quite easily in theories with ``lopsided'' mass matrices for the charged leptons and the down type quarks. A relation connecting the solar and atmospheric neutrino mixing angles is derived, \tan^2\theta_{atm} \simeq 1+ \tan^2\thet...