Inelastically decoupling dark matter

We present a new dark matter candidate, the inelastically decoupling relic (iELDER), which is a cold thermal relic whose abundance is determined by the freeze out of its inelastic scattering off of bath particles in the presence of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mn>3</a:mn> <a:mo stretchy="false">→</a:mo> <a:mn>2</a:mn> </a:math> self-annihilations. The dark matter is predicted to be light, in the <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:mi mathvariant="script">O</d:mi> <d:mo stretchy="false">(</d:mo> <d:mi>MeV</d:mi> <d:mo>−</d:mo> <d:mi>GeV</d:mi> <d:mo stretchy="false">)</d:mo> </d:math> range, with significant self-annihilations and very weak inelastic couplings to ordinary matter. We demonstrate iELDER dark matter using a <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:msub> <i:mi>Z</i:mi> <i:mn>3</i:mn> </i:msub> </i:math> -symmetric toy model as well as quantum chromodynamics (QCD)-like pion theories—the latter showing promising prospects for detection and providing a new benchmark for future searches.