Gamma-ray line constraints on Coy Dark Matter

Abstract

Coy dark matter is an effective scheme in which a fermionic dark matter candidate interacts with the Standard Model fermions via a pseudoscalar mediator. This simple setup avoids the strong constraints posed by direct detection experiments in a natural way and explains, on top of the observed dark matter relic abundance, the spatially extended gamma-ray excess recently detected at the Galactic Center. In this Letter we study the phenomenology of coy dark matter accounting for a novel signature of the model: the diphoton annihilation signal induced by the Standard Model fermions at the loop level. By challenging the model with the observations of spheroidal dwarf satellite galaxies and the results of gamma-ray line searches obtained by the Fermi LAT experiment, we assess its compatibility with the measured dark matter relic abundance and the Galactic Center excesses. We show that despite the gamma-ray line constraint rules out a significant fraction of the considered parameter space, the region connected to the observed Galactic Center excess remains currently viable. Nevertheless, we find that next-generation experiments such as DAMPE, HERD and GAMMA-400 have the potential to probe exhaustively this elusive scenario.

9 pages, 3 figures; references and a footnote added; a latex error corrected

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Cited by in corpus (5)

• Pseudoscalar Mediators: A WIMP model at the Neutrino Floor
• Solar $\gamma$-rays as a Complementary Probe of Dark Matter
• Cornering pseudoscalar-mediated dark matter with the LHC and cosmology
• Modifying dark matter indirect detection signals by thermal effects at freeze-out
• Search for Scalar Dark Matter via Pseudoscalar Portal Interactions: In Light of the Galactic Center Gamma-Ray Excess