The SN 1987A Cooling Bound on Dark Matter Absorption in Electron Targets

TL;DR

This paper derives new bounds from SN 1987A observations on sub-MeV fermionic dark matter interacting with electrons, excluding much of the parameter space relevant for direct detection experiments, including scenarios with light mediators.

Contribution

It provides the first supernova cooling bounds on fermionic dark matter with effective electron couplings, extending analysis to light mediators and showing strong constraints on direct detection parameter space.

Findings

SN 1987A bounds exclude key direct detection regions.

Light mediators can be resonantly produced, affecting constraints.

Combined constraints rule out entire parameter space for direct detection.

Abstract

We present new supernova (SN 1987A) cooling bounds on sub-MeV fermionic dark matter with effective couplings to electrons. These bounds probe the parameter space relevant for direct detection experiments in which dark matter can be absorbed by the target material, showing strong complementarity with indirect searches and constraints from dark matter overproduction. Crucially, our limits exclude the projected sensitivity regions of current and upcoming direct detection experiments. Since these conclusions are a priori not valid for light mediators, we extend our analysis to this case. We show that sub-GeV mediators can be produced resonantly both in supernova cores and in the early Universe, altering the SN 1987A analysis for effective couplings. Still, a combination of supernova cooling constraints and limits from dark matter overproduction excludes the entire parameter space relevant for direct detection in this case.