Is the dark matter interpretation of the EGRET gamma excess compatible with antiproton measurements?

Abstract

We investigate the internal consistency of the halo dark matter model which has been proposed by de Boer et al. to explain the excess of diffuse galactic gamma rays observed by the EGRET experiment. Any model based on dark matter annihilation into quark jets, such as the supersymmetric model proposed by de Boer et al., inevitably also predicts a primary flux of antiprotons from the same jets. Since propagation of the antiprotons in the unconventional, disk-dominated type of halo model used by de Boer et al. is strongly constrained by the measured ratio of boron to carbon nuclei in cosmic rays, we investigate the viability of the model using the DarkSUSY package to compute the gamma-ray and antiproton fluxes. We are able to show that their model is excluded by a wide margin from the measured flux of antiprotons. We therefore find that a model of the type suggested by Moskalenko et al., where the intensities of protons and electrons in the cosmic rays vary with galactic position, is far more plausible to explain the gamma excess.