Future Detection of Supernova Neutrino Burst and Explosion Mechanism

Future detection of a supernova neutrino burst by large underground detectors would give important information for the explosion mechanism of collapse-driven supernovae. We studied the statistical analysis for the future detection of a nearby supernova by using a numerical supernova model and realistic Monte-Carlo simulations of detection by the Super-Kamiokande detector. We mainly discuss the detectability of the signatures of the delayed explosion mechanism in the time evolution of the $\anue$ luminosity and spectrum. For a supernova at 10 kpc away from the Earth, we find that not only the signature is clearly discernible, but also the deviation of energy spectrum from the Fermi-Dirac (FD) distribution can be observed. The deviation from the FD distribution would, if observed, provide a test for the standard picture of neutrino emission from collapse-driven supernovae. For the $D$ = 50 kpc case, the signature of the delayed explosion is still observable, but statistical fluctuation is too large to detect the deviation from the FD distribution. We also propose a method for statistical reconstruction of the time evolution of $\anue$ luminosity and spectrum from data, by which we can get a smoother time evolution and smaller statistical errors than a simple, time-binning analysis. This method is useful especially when the available number of events is relatively small, e.g., a supernova in the LMC or SMC. Neutronization burst of $\nu_e$'s produces about 5 scattering events when $D$ = 10 kpc and this signal is difficult to distinguish from $\anue p$ events.