Neutrino Decoupling Is Altered by Flavor Conversion

TL;DR

This paper presents the first non-linear simulation of neutrino flavor evolution in supernovae, showing that flavor transformation occurs before neutrinos fully decouple, impacting supernova dynamics and nucleosynthesis.

Contribution

It introduces a novel non-linear simulation framework for neutrino flavor evolution including collisions and advection, revealing earlier flavor transformation during decoupling.

Findings

Flavor transformation occurs before neutrino decoupling.

Decoupling surfaces are shifted due to flavor conversion.

Implications for supernova explosion mechanisms and neutrino signals.

Abstract

The large neutrino density in the deep interior of core-collapse supernovae and compact binary merger remnants makes neutrino flavor evolution non-linear because of the coherent forward scattering of neutrinos among themselves. Under the assumption of spherical symmetry, we model neutrino decoupling from matter in an idealized setup and present the first non-linear simulation of flavor evolution in the presence of charged current and neutral current collisions, as well as neutrino advection. Within our framework, we find that flavor transformation occurs before neutrinos fully decouple from matter, dynamically affecting the flavor distributions of all neutrino species and shifting the location of the neutrino decoupling surfaces. Our results call for further work as they may have implications on the explosion mechanism of supernovae, the nucleosynthesis of the heavy elements, as well as the observable neutrino signal, all of which is yet to be assessed.