Supernova deleptonization asymmetry: Impact on self-induced flavor conversion

TL;DR

This paper investigates how the LESA-induced asymmetry in supernova neutrino fluxes affects collective flavor conversion, concluding that such conversion remains suppressed below the shock front despite the asymmetry.

Contribution

It provides a schematic analysis showing that LESA-induced flux asymmetries do not significantly enhance flavor conversion in realistic supernova conditions.

Findings

Self-induced flavor conversion is suppressed below the shock front.

LESA asymmetry does not intersect with realistic supernova profiles.

The instability region for flavor conversion is larger with zero lepton flux.

Abstract

During the accretion phase of a core-collapse supernova (SN), the deleptonization flux has recently been found to develop a global dipole pattern (LESA---Lepton Emission Self-sustained Asymmetry). The $\nu_e$ minus $\bar\nu_e$ flux essentially vanishes in one direction, potentially facilitating self-induced flavor conversion. On the other hand, below the stalled shock wave, self-induced flavor conversion is typically suppressed by multi-angle matter effects, preventing any impact of flavor conversion on SN explosion dynamics. In a schematic model of SN neutrino fluxes, we study the impact of modified $\bar\nu_e$-$\nu_e$ flux asymmetries on collective flavor conversion. In the parameter space consisting of matter density and effective neutrino density, the region of instability with regard to self-induced flavor conversion is much larger for a vanishing lepton number flux, yet this modification does not intersect a realistic SN profile. Therefore, it appears that, even in the presence of LESA, self-induced flavor conversion remains suppressed below the shock front.