Dark matter (DM) annihilation could in principle contribute to the diffuse cosmic gamma-ray background. While with standard assumptions for cosmological and particle physics parameters this contribution is expected to be rather small, a number of processes could boost it, including a larger-than-expected DM annihilation cross section, or the occurrence of DM substructures such as DM minispikes around intermediate-mass black holes. We show that angular correlations of the cosmic gamma-ray background provide a tool to disentangle the signal induced by DM annihilation in minispikes from a conventional astrophysical component. Treating blazars as a known background, we study the prospects for detecting DM annihilations with the Fermi Gamma-Ray Space Telescope for different choices of DM mass and annihilation channels.

• Received 19 December 2008

DOI:https://doi.org/10.1103/PhysRevD.79.043521