Helicity coherence in binary neutron star mergers and non-linear feedback

TL;DR

This paper investigates how helicity coherence affects neutrino flavor conversion in binary neutron star mergers, revealing resonance conditions but limited flavor conversion efficiency due to non-linear feedback.

Contribution

It introduces the role of helicity coherence in neutrino flavor evolution within neutron star mergers and analyzes resonance conditions in this context.

Findings

Resonance conditions for helicity coherence are satisfied in merger scenarios.

Adiabaticity is insufficient for significant flavor conversion.

Multiple MSW-like resonances can occur with non-linear feedback.

Abstract

Neutrino flavor conversion studies based on astrophysical environments usually implement neutrino mixings, neutrino interactions with matter and neutrino self-interactions. In anisotropic media, the most general mean-field treatment includes neutrino mass contributions as well, that introduce a coupling between neutrinos and antineutrinos termed helicity or spin coherence. We discuss resonance conditions for helicity coherence for Dirac and Majorana neutrinos. We explore the role of these mean-field contributions on flavor evolution in the context of a binary neutron star merger remnant. We find that resonance conditions can be satisfied in neutron star merger scenarios while adiabaticity is not sufficient for efficient flavor conversion. We analyse our numerical findings by discussing general conditions to have multiple MSW-like resonances, in presence of non-linear feedback, in astrophysical environments.