SIMPle Dark Matter: Self-Interactions and keV Lines

TL;DR

This paper proposes a simple supersymmetric hidden sector model where dark matter consists of hidden glueballinos and glueballs, explaining small-scale structure and the 3.5 keV X-ray line through hyperfine splitting and radiative decays.

Contribution

It introduces a minimal supersymmetric hidden sector with specific mass scales that naturally accounts for dark matter relic density, self-interactions, and observed X-ray signals.

Findings

Glueballinos have the correct relic density at TeV scale.

Self-interactions resolve small-scale structure issues.

Radiative decays produce the 3.5 keV X-ray line.

Abstract

We consider a simple supersymmetric hidden sector: pure SU(N) gauge theory. Dark matter is made up of hidden glueballinos with mass $m_X$ and hidden glueballs with mass near the confinement scale $\Lambda$. For $m_X \sim 1\,\text{TeV}$ and $\Lambda \sim 100\,\text{MeV}$, the glueballinos freeze out with the correct relic density and self-interact through glueball exchange to resolve small-scale structure puzzles. An immediate consequence is that the glueballino spectrum has a hyperfine splitting of order $\Lambda^2 / m_X \sim 10\,\text{keV}$. We show that the radiative decays of the excited state can explain the observed 3.5 keV X-ray line signal from clusters of galaxies, Andromeda, and the Milky Way.