SUPERNOVA NEUTRINOS AND THE NU(TAU) MASS

We perform an extensive investigation of the sensitivity to non-vanish ing nu(tau) mass in a large water Cerenkov detector, developing an ana lysis method for neutrino events originated by a supernova explosion. This approach, based on directional considerations, provides informati on almost independent of the supernova model. We analyze several theor etical models from numerical simulations and phenomenological models b ased on SN1987A data, and determine optimal values of the analysis par ameters so as to reach the highest sensitivity to a non-vanishing nu(t au) mass. The minimal detectable mass is generally just above the cosm ologically interesting range, m similar to 100 eV, in the case of a su pernova explosion near the galactic center. For the case that no posit ive signal is obtained, observation of a neutrino burst with Super-Kam iokande will anyhow lower the present upper bound on nu(tau) mass to f ew hundred eV. (C) 1997 Elsevier Science B.V.