Neutrino halo effect on collective neutrino oscillation in iron core-collapse supernova model of a 9.6 $M_{\odot}$ star

TL;DR

This study investigates how the neutrino halo influences collective neutrino oscillations in a 9.6 solar mass star's core-collapse supernova, revealing timing-dependent effects and spectral feature modifications.

Contribution

It extends the multi-angle computational framework to include neutrino halo effects, demonstrating their impact on oscillation timing and spectral features in supernova models.

Findings

Neutrino halo causes delays in oscillation onset.

Halo effects lead to sharper spectral features.

Oscillation suppression varies with epoch and radius.

Abstract

We extend the multi-angle computational framework and investigate the time evolution of the neutrino halo on collective neutrino oscillation in the core collapse of an iron core progenitor. We find that in the case of the $9.6\, \rm M_\odot$ progenitor adopted in this work, there are windows of time when the effects of neutrino halo and collective neutrino oscillation are not simultaneously large. Inside the shock, the impact of the inward-scattered halo neutrino cannot in general be neglected compared to the outward-propagating neutrino flux. However, during early epochs, collective neutrino oscillation is effectively shut down by multi-angle matter suppression. During the intermediate epoch, collective neutrino oscillation is not suppressed, but its onset radius is beyond the still relatively small explosion shock front where the halo is prominent. We also find in the case of the $9.6\, \rm M_\odot$ progenitor the halo neutrinos induce a delay in the onset of collective neutrino oscillations. This causes novel flavor conversions which sharpen collective neutrino oscillation spectral features. We predict that the inclusion of neutrino halo effects makes neutrino signals that are more clearly distinct from thermal emission that when halo neutrinos are omitted.