Signal for SupernovaνμandντNeutrinos in Water Čerenkov Detectors

We suggest that photons with energies between 5 and 10 MeV, generated by the ( $\nu ,{\nu }^{\prime }p\gamma$) and ( $\nu ,{\nu }^{\prime }n\gamma$) reactions on ${}^{16}\mathrm{O}$, constitute a signal which allows a unique identification of supernova ${\nu }_{\mu }$ and ${\nu }_{\tau }$ neutrinos in water Čerenkov detectors. We calculate the yield of such $\gamma$ events and estimate that a few hundred of them would be detected in Superkamiokande for a supernova at 10 kpc distance.