3 NEUTRINO DELTA-M(2) SCALES AND THE SINGULAR SEESAW MECHANISM - ART.NO. 093003

It is shown that the singular seesaw mechanism can simultaneously expl ain all the existing data supporting nonzero neutrino masses and mixin g. The three mass-squared differences that are needed to accommodate t he atmospheric neutrino data (through nu(mu) - nu(s) oscillation), the solar neutrino data via the MSW mechanism (through nu(e) - v(tau) osc illation), and the positive result of nu(mu) - nu(e) oscillation from the LSND can be generated by this mechanism, whereas the vacuum oscill ation solution to the solar neutrino problem is disfavored. We find th at the electron and tau neutrino masses are of the order of 10(-3) eV, and the muon neutrino and a sterile neutrino an almost maximally mixe d to give a mass of the order of 1 eV. Two heavy sterile neutrinos hav e a mass of the order of 1 keV which can be obtained by the double see saw mechanism with an intermediate mass scale similar to 10(5) GeV. A possible origin of such a scale is discussed. [S0556-2821(98)04917-0].