Mass signature of supernova {nu}{sub {mu}} and {nu}{sub {tau}} neutrinos in SuperKamiokande

The {nu}{sub {mu}} and {nu}{sub {tau}} neutrinos (and their antiparticles) from a Galactic core-collapse supernova can be observed in a water-{hacek C}erenkov detector by the neutral-current excitation of {sup 16}O. The number of events expected is several times greater than from neutral-current scattering on electrons. The observation of this signal would be a strong test that these neutrinos are produced in core-collapse supernovae, and with the right characteristics. In this paper, this signal is used as the basis for a technique of neutrino mass determination from a future Galactic supernova. The masses of the {nu}{sub {mu}} and {nu}{sub {tau}} neutrinos can either be measured or limited by their delay relative to the {bar {nu}}{sub e} neutrinos. By comparing to the high-statistics {bar {nu}}{sub e} data instead of the theoretical expectation, much of the model dependence is canceled. Numerical results are presented for a future supernova at 10thinspkpc as seen in the SuperKamiokande detector. Under reasonable assumptions, and in the presence of the expected counting statistics, {nu}{sub {mu}} and {nu}{sub {tau}} masses down to about 50thinspeV can be simply and robustly determined. The signal used here is more sensitive to small neutrino masses than the signal based on neutrino-electron scattering. {copyright}more » {ital 1998} {ital The American Physical Society}« less