A see-saw model for atmospheric and solar neutrino oscillations

We have constructed an explicit see-saw model containing two singlet neutrinos, one carrying a (B−3Le) gauge charge with an intermediate mass scale of ∼O(1010) GeV along with a sterile one near the GUT (grand unification theory) scale of ∼O(1016) GeV. With these mass scales and a reasonable range of Yukawa couplings, the model can naturally account for the near-maximal mixing of atmospheric neutrino oscillations and the small mixing matter-enhanced oscillation solution to the solar neutrino deficit.