The SIMPlest Miracle

TL;DR

This paper presents explicit strongly coupled gauge theories, similar to QCD, where pions act as dark matter particles through 3-to-2 interactions, providing a concrete realization of the SIMP mechanism that influences structure formation.

Contribution

It introduces specific QCD-like theories with calculable 3-to-2 and 2-to-2 processes, demonstrating a viable strongly-interacting dark matter model.

Findings

Explicit models of strongly coupled gauge theories with dark matter pions.

Derived relationship between 3-to-2 and 2-to-2 scattering rates.

Implications for dark matter relic abundance and structure formation.

Abstract

It has recently been proposed that dark matter could be a thermal relic of 3-to-2 scatterings in a strongly coupled hidden sector. We present explicit classes of strongly coupled gauge theories that admit this behavior. These are QCD-like theories of dynamical chiral symmetry breaking, where the pions play the role of dark matter. The number-changing 3-to-2 process, which sets the dark matter relic abundance, arises from the Wess-Zumino-Witten term. The theories give an explicit relationship between the 3-to-2 annihilation rate and the 2-to-2 self-scattering rate, which alters predictions for structure formation. This is a simple calculable realization of the strongly-interacting-massive-particle (SIMP) mechanism.