Bi-maximal Neutrino Mixing Pattern Reexamined

The simplest unified extension of the Minimal Supersymmetric Standard Model with bi-linear R--Parity violation provides a predictive scheme for neutrino masses which can account for the observed atmospheric and solar neutrino anomalies in terms of bi-maximal neutrino mixing. The maximality of the atmospheric mixing angle arises dynamically, by minimizing the scalar potential, while the solar neutrino problem can be accounted for either by large or by small mixing oscillations...

We point out two simple but instructive possibilities to modify the tri-bimaximal neutrino mixing ansatz, such that leptonic CP violation can naturally be incorporated into the resultant scenarios of nearly tri-bimaximal flavor mixing. The consequences of two new ansaetze on solar, atmospheric and reactor neutrino oscillations are analyzed. We also discuss an interesting approach to construct lepton mass matrices under permutation symmetry, from which one may derive another n...

We find a grand unified SO(10) model which accommodates the bi-maximal neutrino mixing for vacuum-oscillation solutions to the atmospheric and the solar neutrino problems. This model maintains the original SO(10) mass relation between neutrino and up-type quark masses, $m_{\nu_2} / m_{\nu_3} \sim (m_{c}/m_{t})^2$.

The usual Bi-Maximal (BM) neutrino mixing faces an inherent problem in lowering the solar mixing angle below $\tan^{2}\theta_{12}=0.50$ when charged lepton correction is taken. This minimum $\theta_{12}$ is achievable only if CP violation is absent. We start with a new model which incorporates a new idea of mixing developed recently, called Bi-Large (BL) mixing, similar to BM mixing execpt that the former chooses rather $\theta_{13}$ as Cabibbo angle $(\theta_c)$ than zero. W...

We study the simplest Standard Model estension with only one extra right-handed neutrino. In this case there are two massless $m_{1,2}$ and two massive $m_{3,4}$ neutrinos, and in principle both solar and atmospheric anomalies can be described in two different scenarios, $m_3 << m_4$ (scheme I) and $m_3 \simeq m_4$ (scheme II). However, neither bi-maximal mixing nor the dark matter problem are explained in this minimal extension. Only scheme II can accommodate simultaneously ...

We describe how bi-maximal neutrino mixing can be realized in realistic models based on MSSM and SUSY GUTs such as SU(5) and SO(10). A crucial role is played by an anomalous ${\cal U}(1)$ flavor symmetry, which also helps understand the observed charged fermion mass hierarchies and the magnitudes of the CKM matrix elements. While in MSSM a variety of solutions for the solar neutrino puzzle are possible, SUSY SU(5) and SO(10) only permit the large mixing angle MSW solution. Mo...

Inspired by the atmospheric multi-GeV neutrino data, we consider neutrino flavor mixing matrices which are maximal in a $2\times 2$ subsector. This condition is a strong restriction: the full matrix including complex phases depends essentially on one parameter. The survival probability is an universal function of $L/E$, independent of generation, in the region of interest for the accelerator and atmospheric experiments. It is possible with the solar neutrino data alone to rec...

We show how a unified description of the various two-flavor neutrino oscillation solutions, allowed by the atmospheric and solar neutrino experiments, are naturally realized within the framework of $\nu$MSSM (MSSM augmented with the seesaw mechanism) and beyond, especially grand unified theories. A general mechanism for achieving maximal mixing to resolve the atmospheric anomaly is discussed, and applied to the flipped SU(5) model. Except in the case of MSSM and SU(5), a ligh...

We present neutrino mass matrices which predict the atmospheric neutrino mixing to be almost maximal, $\sin^2 2\theta_{atm}>0.999$, as well as the large solar neutrino mixing, $8/9>\sin^2 2\theta_{sol}>0.87$, and the large CP violation (the CP violation phase in the standard form is maximal $\delta=\pi/2$), based on the $Z_3$ symmetry.

The SuperKamiokande data on atmospheric neutrinos imply that $\nu_{\mu}$ has large (or even maximal) mixing. It is still open question whether this mixing is the flavor one or mixing with singlet state (sterile neutrino). Several tests exist to establish the channel of atmospheric neutrino oscillations. Large mixing can be a property of the second and third generations, so that the scheme with single large mixing is realized. It can be a generic property of all leptons, thus ...