Light Chiral Dark Sector

TL;DR

This paper proposes a natural model where dark matter is a composite pseudo Nambu-Goldstone boson arising from a non-Abelian gauge sector, with potential explanations for dark matter and muon g-2 anomalies, and distinctive collider signatures.

Contribution

It introduces a minimal, natural model of light chiral dark sector with composite dark pions, linking dark matter, dark photon, and muon g-2, with specific experimental signatures.

Findings

The model's parameter space allows for dark matter consistent with cosmological constraints.

It can potentially explain the muon g-2 discrepancy.

Distinctive collider signatures include monophoton events and dark rho meson production.

Abstract

An interesting possibility for dark matter is a scalar particle of mass of order 10 MeV-1 GeV, interacting with a U(1) gauge boson (dark photon) which mixes with the photon. We present a simple and natural model realizing this possibility. The dark matter arises as a composite pseudo Nambu-Goldstone boson (dark pion) in a non-Abelian gauge sector, which also gives a mass to the dark photon. For a fixed non-Abelian gauge group, SU(N), and a U(1) charge of the constituent dark quarks, the model has only three free parameters: the dynamical scale of the non-Abelian gauge theory, the gauge coupling of the dark photon, and the mixing parameter between the dark and standard model photons. In particular, the gauge symmetry of the model does not allow any mass term for the dark quarks, and stability of the dark pion is understood as a result of an accidental global symmetry. The model has a significant parameter space in which thermal relic dark pions comprise all of the dark matter, consistently with all experimental and cosmological constraints. In a corner of the parameter space, the discrepancy of the muon g-2 between experiments and the standard model prediction can also be ameliorated due to a loop contribution of the dark photon. Smoking-gun signatures of the model include a monophoton signal from the e+ e- collision into a photon and a "dark rho meson." Observation of two processes in e+ e- collision, the mode into the dark photon and that into the dark rho meson, would provide strong evidence for the model.