Self-refraction of supernova neutrinos: mixed spectra and three-flavor instabilities

TL;DR

This paper investigates three-flavor neutrino flavor transformations in supernovae, revealing new spectral swap patterns and mixed spectra during the cooling phase, especially under the inverted mass hierarchy.

Contribution

It introduces a comprehensive three-flavor analysis of supernova neutrino oscillations, uncovering novel spectral features not seen in two-flavor models.

Findings

Distinct spectral swap patterns in three-flavor spectra

Discovery of mixed spectra for antineutrinos

Identification of flavor evolution instabilities

Abstract

Neutrinos in a core-collapse supernova undergo coherent flavor transformations in their own background. We explore this phenomenon during the cooling stage of the explosion. Our three-flavor calculations reveal qualitatively new effects compared to a two-flavor analysis. These effects are especially clearly seen for the inverted mass hierarchy: we find a different pattern of spectral "swaps" in the neutrino spectrum and a novel "mixed" spectrum for the antineutrinos. A brief discussion of the relevant physics is presented, including the instability of the two-flavor evolution trajectory, the 3-flavor pattern of spectral "swaps," and partial nonadiabaticity of the evolution.