Minimal see-saw model for atmospheric and solar neutrino oscillations

Abstract

We present a minimal see-saw model based on an extension of the standard model (SM) which includes an additional U(1), with gauge charge B-3/2(L_μ+L_T). The requirement of anomaly cancellation implies the existence of two right-handed singlet neutrinos, carrying this gauge charge, which have normal Dirac couplings to ν_μ and ν_T but suppressed ones to ν_e. Assuming the U(1) symmetry breaking scale to be 10¹²⁻¹⁶ GeV, this model can naturally account for the large (small) mixing solutions to the atmospheric (solar) neutrino oscillations.