Supernova bound on keV-mass sterile neutrinos reexamined

TL;DR

This paper reexamines supernova constraints on keV-mass sterile neutrinos, highlighting how matter effects and asymmetries influence their emission and the resulting bounds, especially in the warm dark matter mass range.

Contribution

It provides a detailed analysis of supernova bounds on sterile neutrinos, considering matter effects and asymmetries, and clarifies constraints in the keV mass range.

Findings

Constraints are strong for m_s > 100 keV to prevent excessive energy loss.

Matter effects suppress mixing angles for smaller m_s, except at resonances.

In the 1-10 keV range, mixing angles are largely unconstrained.

Abstract

Active-sterile neutrino mixing is strongly constrained for m_s > 100 keV to avoid excessive energy losses from supernova cores. For smaller m_s, matter effects suppress the effective mixing angle except for a resonant range of energies where it is enhanced. We study the case of \nu_tau-\nu_s-mixing where a \nu_tau-\bar\nu_tau asymmetry builds up due to the strong excess of \nu_s over \bar\nu_s emission or vice versa, reducing the overall emission rate. In the warm dark matter range m_s < 10 keV the mixing angle is essentially unconstrained.