Three-flavor collective neutrino conversions with multi-azimuthal-angle instability in an electron-capture supernova model

TL;DR

This paper demonstrates that multi-azimuthal angle effects induce new collective neutrino flavor conversions in supernovae, significantly impacting neutrino signals detected on Earth, especially when axial symmetry is broken.

Contribution

It introduces the three-dimensional MAA effect into supernova neutrino oscillation models, revealing new flavor conversion phenomena absent under axial symmetry assumptions.

Findings

MAA effect causes flavor conversions at previously suppressed epochs.

The onset of oscillations correlates with flavor instability growth.

Neutrino detection signals are notably altered by MAA effects.

Abstract

We investigate the multi-azimuthal angle (MAA) effect on collective neutrino oscillation by considering the three-dimensional neutrino momentum distribution in a realistic electron-capture supernova model with an $8.8 M_{\odot}$ progenitor. We find that the MAA effect induces collective flavor conversions at epochs when it is completely suppressed under the axial-symmetric approximation. This novel activity is switched on/off by the growth of the MAA instability and imprints additional time evolution in the expected neutrino event rate. We validate our results by extending the linear stability analysis into the three-flavor scheme including mixing angles, and confirm that the onset of collective neutrino oscillation matches the steep growth of flavor instability. We discuss how the MAA effect alters neutrino detection at Super-Kamiokande and DUNE.