When do supernova neutrinos of different flavors have similar luminosities but different spectra? |
| |
Authors: | H -Thomas Janka |
| |
Institution: | Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Avenue, Chicago, IL 60637, USA |
| |
Abstract: | Muon and tau neutrinos (νx) interact with protoneutron star matter only via neutral currents and exchange energy with the stellar gas predominantly by neutrino-electron scattering and neutrino-pair processes. In contrast, electron neutrinos and antineutrinos (νe and
) are frequently absorbed and produced in charged-current mediated reactions with nucleons. Therefore the emergent νe and
originate from layers with lower temperatures further out in the star and are emitted with much lower characteristic spectral temperatures. In addition, a major contribution to the νe and
opacities is due to absorptions, while the opacity of νx is strongly dominated by scattering reactions with nucleons and nuclei in which the νx energy is (essentially) conserved. Therefore the νx distribution is nearly isotropic when νx decouple energetically and their outward diffusion is slowed down. In a generalized form to include this effect, the Stefan-Boltzmann Radiation Law can account for both the facts that νe (
) and νx emerge from the star with similar luminosities but with very different characteristic spectral temperatures. Simple analytical expressions to estimate the effect are given. If, as recently argued, even at densities significantly below nuclear matter density neutral-current scatterings were associated with considerable energy transfer between neutrino and target particle, one might expect spectral temperatures of νx much closer to those of νe and
. This is of relevance for the detection of neutrino signals from supernovae. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|