Spontaneous Breaking of Flavor Symmetry and Naturalness of Nearly Degenerate Neutrino Masses and Bi-maximal Mixing

Abstract

The gauge model with $SO(3{)}_F$ flavor symmetry and three Higgs triplets is studied. We show how the intriguing nearly degenerate neutrino mass and bi-maximal mixing scenario comes out naturally after spontaneous breaking of the symmetry. The hierarchy between the neutrino mass-squared differences, which is needed for reconciling both solar and atmospheric neutrino data, is naturally resulted from an approximate permutation symmetry. The model can also lead to interesting phenomena on lepton-flavor violations via the $SO(3{)}_F$ gauge interactions.

Comments: 13 pages, latex, no figures, the version appearing in SCIENCE IN CHINA (Series A), Vol.35 No.9 (2000)