Bimaximal neutrino mixings from lopsided mass matrices

Current solar and atmospheric neutrino oscillation data seem to favor a bimaximal pattern for neutrino mixings where the matrix elements Ue2 and Uμ3 are of order one, while Ue3 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, tan2θatm≃1+tan2θsol, which predicts sin22θatm≃0.97 corresponding to the best fit LMA solution for solar neutrinos. Predictive schemes in SO(10) realizing these ideas are presented. A new class of SO(10) models with lopsided mass matrices is found which makes use of an adjoint VEV along the I3R direction, rather than the traditional B−L direction.