Predictive Schemes for Bimaximal Neutrino Mixings

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 Le −Lμ −Lτ 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. A one parameter model describing all neutrino data is presented, which predicts Ue3 ≃ √ me/mτ ≃ 0.017. A second two parameter scheme predicts Ue3 to be vanishingly small. We also show how these scenarios can be extended to accommodate the LSND observations within a 3+1 neutrino oscillation scheme by including a mirror sector of particles and forces.