Mass signature of supernova νμ and ντ neutrinos in SuperKamiokande

The νμ and ντ neutrinos (and their antiparticles) from a Galactic core-collapse supernova can be observed in a water-Čerenkov detector by the neutral-current excitation of 16O. 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 νμ and ντ neutrinos can either be measured or limited by their delay relative to the ν̅e neutrinos. By comparing to the high-statistics ν̅e data instead of the theoretical expectation, much of the model dependence is canceled. Numerical results are presented for a future supernova at 10 kpc as seen in the SuperKamiokande detector. Under reasonable assumptions, and in the presence of the expected counting statistics, νμ and ντ masses down to about 50 eV 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