Galactic Center Gamma-Ray Excess through a Dark Shower

Abstract

The reported excess of $\gamma$-rays, emitted from an extended region around the galactic center, has a distribution and rate suggestive of an origin in dark matter (DM) annihilations. The conventional annihilation channels into standard model (SM) $b$ quarks or $\tau$ leptons may, however, be in tension with various experimental constraints on antiproton and positron fluxes. We present a framework that is free from such constraints. The key idea is that the mediators between the dark matter and the SM are themselves part of a strongly coupled sector: a hidden valley. In this scenario, the dark matter particles annihilate only into hidden quarks that subsequently shower and hadronize. Hidden quark effective couplings to SM hypercharge allow the lightest hidden bound states to subsequently decay into SM photons, producing the observed photon energy spectrum. Associated production of SM fermions is, in contrast, suppressed by electroweak, loop or helicity effects. We find that, generically, $\sim$ 10 GeV DM and a confinement scale $\sim$ 1 GeV provide a good fit to the observed spectrum. An $SU(2)$ hidden confining group is preferred over $SU(3)$ or higher rank gauge groups, up to uncertainties in the extraction of the astrophysical background. An explicit realization of this framework is also presented, and its phenomenology is discussed in detail, along with pertinent cosmological, astrophysical and collider bounds. This framework may be probed by model-independent searches, including future beam-dump experiments.

9 pages, 4 figures, v2: references added, description of simulations clarified, PRD version

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Cited by in corpus (8)

• A Tale of Tails: Dark Matter Interpretations of the Fermi GeV Excess in Light of Background Model Systematics
• A taste of dark matter: Flavour constraints on pseudoscalar mediators
• WIMPs at the Galactic Center
• Multi-Step Cascade Annihilations of Dark Matter and the Galactic Center Excess
• Dynamical Dark Matter from Strongly-Coupled Dark Sectors
• Galactic Centre GeV Photons from Dark Technicolor
• The Semi-Hooperon: Gamma-ray and anti-proton excesses in the Galactic Center
• Point Sources from Dissipative Dark Matter