3-GENERATION NEUTRINO MIXING AND LSND DARK-MATTER NEUTRINOS

The reported signal at the LSND experiment, when interpreted as neutri no mixing with delta m(2) = 6 eV(2), provides evidence for neutrinos w ith a cosmologically significant mass. However, attempts to reconcile this interpretation of the experiment with other hints about neutrino properties require a (sterile) fourth neutrino and/or an ''inverted'' neutrino mass hierarchy. An interpretation of the LSND experiment empl oying delta m(2) = 0.3 eV(2), with three-generation mixing and a ''nor mal'' neutrino mass hierarchy, can just barely be reconciled with the negative results of other laboratory neutrino oscillation experiments and the positive hints of neutrino oscillation from the solar and atmo spheric neutrino problems. Though subject to test by by future experim ents, such a solution allows (but does not demand) neutrino masses rel evant for dark matter.