Multiple Spectral Splits of Supernova Neutrinos

Abstract

Collective oscillations of supernova neutrinos swap the spectra ${f}_{{\ensuremath{\nu}}_{e}}(E)$ and ${f}_{{\overline{\ensuremath{\nu}}}_{e}}(E)$ with those of another flavor in certain energy intervals bounded by sharp spectral splits. This phenomenon is far more general than previously appreciated: typically one finds one or more swaps and accompanying splits in the $\ensuremath{\nu}$ and $\overline{\ensuremath{\nu}}$ channels for both inverted and normal neutrino mass hierarchies. Depending on an instability condition, swaps develop around spectral crossings (energies where ${f}_{{\ensuremath{\nu}}_{e}}={f}_{{\ensuremath{\nu}}_{x}}$, ${f}_{{\overline{\ensuremath{\nu}}}_{e}}={f}_{{\overline{\ensuremath{\nu}}}_{x}}$ as well as $E\ensuremath{\rightarrow}\ensuremath{\infty}$ where all fluxes vanish), and the widths of swaps are determined by the spectra and fluxes. Washout by multiangle decoherence varies across the spectrum and splits can survive as sharp spectral features.