Chiral Dark Sector

TL;DR

This paper introduces a simple dark sector model where dark matter is composed of composite states from hidden strong dynamics, with rich phenomenology including potential detection signals and dark radiation.

Contribution

The model uniquely links dark matter stability to accidental symmetries and explores phenomenology with a minimal parameter set, including a kinetic mixing portal.

Findings

Dark matter can be a mixture of dark pion and dark baryon detectable via experiments.

Large Hadron Collider can potentially discover the $U(1)_D$ gauge boson.

Dark pion can act as dark radiation, correlated with dark matter detection signals.

Abstract

We present a simple and natural dark sector model in which dark matter particles arise as composite states of hidden strong dynamics and their stability is ensured by accidental symmetries. The model has only a few free parameters. In particular, the gauge symmetry of the model forbids the masses of dark quarks, and the confinement scale of the dynamics provides the unique mass scale of the model. The gauge group contains an Abelian symmetry $U(1)_D$, which couples the dark and standard model sectors through kinetic mixing. This model, despite its simple structure, has rich and distinctive phenomenology. In the case where the dark pion becomes massive due to $U(1)_D$ quantum corrections, direct and indirect detection experiments can probe thermal relic dark matter which is generically a mixture of the dark pion and the dark baryon, and the Large Hadron Collider can discover the $U(1)_D$ gauge boson. Alternatively, if the dark pion stays light due to a specific $U(1)_D$ charge assignment of the dark quarks, then the dark pion constitutes dark radiation. The signal of this radiation is highly correlated with that of dark baryons in dark matter direct detection.