A Minimal See-Saw Model for Hierarchical Neutrino Masses with Large Mixing

Abstract

The atmospheric and solar neutrino oscillation data suggest hierarchical neutrino masses with at least one large mixing. The simplest see-saw models for reconciling the two features are U(1) extensions of the SM with flavour dependent gauge charges. I discuss a minimal model of this type containing two heavy right-handed neutrinos, which have normal Dirac couplings to ${\nu }_{\mu }$ and ${\nu }_{\tau }$ but suppressed ones to ${\nu }_e$. It can naturally account for the large (small) mixing solutions to the atmospheric (solar) neutrino oscillation data.

Comments: 6 pages, Latex, Invited Talk at the 6th San Miniato Topical Seminar on `Neutrino and Astroparticle Physics', to appear in Nuclear Physics B (Proc. Suppl.)