Dark Matter, Shared Asymmetries, and Galactic Gamma Ray Signals

Abstract

We introduce a novel dark matter scenario where the visible sector and the dark sector share a common asymmetry. The two sectors are connected through an unstable mediator with baryon number one, allowing the standard model baryon asymmetry to be shared with dark matter via semi-annihilation. The present-day abundance of dark matter is then set by thermal freeze-out of this semi-annihilation process, yielding an asymmetric version of the WIMP miracle as well as promising signals for indirect detection experiments. As a proof of concept, we find a viable region of parameter space consistent with the observed Fermi excess of GeV gamma rays from the galactic center.

20+12 pages, 11 figures, 1 table; v2: references added, minor corrections to CMB bounds; v3: footnotes added for clarification, updated appendix A, conclusions unchanged, version to appear in JCAP