Supernova Neutrino Spectra and Applications to Flavor Oscillations

Abstract

We study the flavor-dependent neutrino spectra formation in the core of a supernova (SN) by means of Monte Carlo simulations. A high-statistics neutrino signal from a galactic SN may contain information that severely constrains the parameter space for neutrino oscillations. Therefore, reliable predictions for flavor-dependent fluxes and spectra are urgently needed. In all traditional hydrodynamic simulations the nu_mu,tau and nu_mu,tau-bar interactions commonly included are rather schematic. With our Monte Carlo simulations we find that the most relevant sources for nu_mu,tau and nu_mu,tau-bar are traditionally not included. In comparing our numerical results for all flavors we find the standard hierarchy of mean energies nu_e < nu_e-bar < nu_mu,tau, with, however, very similar values for nu_mu,tau and nu_e-bar. The luminosities of nu_mu,tau and nu_mu,tau-bar can differ by up to a factor of 2 from L_nue-bar and L_nue, the latter two are very similar. The Garching Group obtains similar results from their self-consistent simulation with the full set of interactions. These results are almost orthogonal to the previous standard picture of exactly equal luminosities of all flavors and differences in mean energies of up to a factor of 2. Existing concepts for identifying oscillation effects in a SN neutrino signal need to be revised. We present two methods for detecting the earth-matter effect that are rather independent of predictions from SN simulations.