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

Abstract

We investigate the internal consistency of the halo dark matter model which has beenproposed by de Boer et al for explaining the excess of diffuse galactic gamma raysobserved by the EGRET experiment. Any model based on dark matter annihilationinto 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. Sincepropagation of the antiprotons in the unconventional, disc-dominated type ofhalo model used by de Boer et al is strongly constrained by the measured ratio ofboron to carbon nuclei in cosmic rays, we investigate the viability of the modelusing 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 themeasured flux of antiprotons. We therefore find that a model of the type suggested byMoskalenko et al, where the intensities of protons and electrons in the cosmic rays varywith galactic position, is far more plausible for explaining the gamma excess.