Supernova Neutrino Spectra and Applications to Flavor Oscillations

TL;DR

This study uses Monte Carlo simulations to analyze supernova neutrino spectra formation, revealing new insights into flavor-dependent fluxes and spectra, which are crucial for understanding neutrino oscillations and interpreting supernova signals.

Contribution

The paper introduces detailed Monte Carlo simulations that incorporate previously neglected interactions, providing more accurate predictions of supernova neutrino spectra and fluxes, challenging standard assumptions.

Findings

Nu_mu,tau and nu_mu,tau-bar interactions are more significant than previously modeled.

The hierarchy of mean energies is nu_e < nu_e-bar < nu_mu,tau, with nu_mu,tau and nu_e-bar having similar energies.

Luminosities of nu_mu,tau and nu_mu,tau-bar can differ substantially from nu_e and nu_e-bar.

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.