Monte Carlo simulations of neutrino transport in type II supernovae.

Based on a hydrodynamical model of stellar collapse, spectra and luminosities of neutrinos of various flavors are computed by means of a direct Monte Carlo simulation of neutrino transport. It is shown that local emission and absorption in shocked mater dominates the neutrino flux for at least several tenths of a second after core bounce. The average energy of electron neutrinos drops from about 10 MeV shortly after core bounce to about 8 MeV within 30 msec. Electron antineutrinos leave the star with a mean energy of 14 MeV, while muon and tauon neutrinos have 16-17 MeV at these early stages of the protoneutron star cooling. The typical time scales for stationary flux patterns to develop in the shocked stellar regions are less than 1 msec for electron neutrinos and about 3 to 4 msec for muon and tauon neutrinos.