Type II Seesaw and a Gauge Model for the Bimaximal Mixing Explanation of Neutrino Puzzles

Abstract

We present a gauge model for the bimaximal mixing pattern among the neutrinos that 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. A combination of global $L_e-L_μ-L_τ$ and $S_3$ symmetries constrain the mass matrix for both charged leptons and neutrinos in such a way that the bimaximal pattern emerges naturally at the tree level and needed splittings among neutrinos at the one loop level. This model predicts observable branching ratios for $τ\to μμμ$, which could be used to test it.