Multi-angle effects in collective supernova neutrino oscillations

TL;DR

This paper investigates how angular effects influence collective neutrino oscillations in supernovae, revealing conditions for coherence or decoherence that impact observable neutrino signals.

Contribution

It introduces an analysis of multi-angle effects in supernova neutrino oscillations, highlighting the conditions for coherence and decoherence in a nonlinear system.

Findings

Multi-angle effects can cause either decoherence or coherence in neutrino flavor oscillations.

The system exhibits abrupt switching between self-maintained coherence and decoherence.

Realistic supernova conditions likely favor quasi single-angle behavior, simplifying analysis.

Abstract

We study two-flavor collective neutrino oscillations in the dense-neutrino region above the neutrino sphere in a supernova (SN). The angular dependence of the neutrino-neutrino interaction potential causes "multi-angle" effects that can lead either to complete kinematical decoherence in flavor space or only to small differences between different trajectories. This nonlinear system switches abruptly between "self-maintained coherence" and "self-induced decoherence" among the angular modes, depending on the strength of the deleptonization flux. For a realistic SN the quasi single-angle behavior is probably typical, simplifying the numerical treatment and probably allowing for the survival of observational features of flavor oscillations.