Signal for Supernova ν μ and ν τ Neutrinos in Water Čerenkov Detectors

We suggest that photons with energies between 5 and 10 MeV, generated by the ( ν,ν′pγ) and ( ν,ν′nγ) reactions on 16O, constitute a signal which allows a unique identification of supernova νμ and ντ neutrinos in water Cerenkov detectors. We calculate the yield of such γ events and estimate that a few hundred of them would be detected in Superkamiokande for a supernova at 10 kpc distance.