Type II seesaw and a gauge model for the bimaximal mixing explanation of neutrino puzzles

Abstract

We present an extension of the standard model where the bimaximal mixing pattern among the neutrinos naturally arises via the type II seesaw mechanism. This explains both the atmospheric and solar neutrino data via large angle vacuum oscillation among the three known neutrinos. The model does not include righthanded neutrinos but additional Higgs triplets which acquire naturally small vev's due to the type II seesaw mechanism. The presence of a global L e − L μ − L τ and S 3 symmetry leads naturally to the desired mass splittings among neutrinos at the one loop level. This model predicts observable branching ratios for τ→ μμμ, which could be used to test the model.