Is Dark Matter visible by Galactic Gamma Rays?

Abstract

Dark Matter annihilation (DMA) is expected to yield an excess of gamma rays and antimatter particles, like antiprotons and positrons, above the background from cosmic ray interactions. Recently it was shown that the observed excess of diffuse Galactic gamma rays above 1 GeV shows all the features expected from DMA, especially the excess traces the Dark Matter halo, as proven by reconstructing the peculiar shape of the rotation curve of our Galaxy from the gamma ray excess. However, it was claimed by Bergstrom et al. that the DMA interpretation of the EGRET gamma ray excess is incompatible with the antiproton fluxes, since in their propagation model with isotropic diffusion the flux of antiprotons would be far beyond the observed flux. Here it is shown that anisotropic propagation can reduce the antiproton yield by an order of magnitude, while still being consistent with the B/C ratio. Therefore antiprotons cannot prove or disprove the existence of light DM particles, since the background and signal have very similar antiproton spectra.