GALACTIC DIFFUSION AND THE ANTIPROTON SIGNAL OF SUPERSYMMETRIC DARK-MATTER

The leaky box model is now ruled out by measurements of a cosmic ray g radient throughout the galactic disk. It needs to be replaced by a mor e refined treatment which takes into account the diffusion of cosmic r ays in the magnetic fields of the Galaxy. We have estimated the flux o f antiprotons on the Earth in the framework of a two-zone diffusion mo del. Those species are created by the spallation reactions of high-ene rgy nuclei with the interstellar gas. Another potential source of anti protons is the annihilation of supersymmetric particles in the dark ha lo that surrounds our Galaxy. In this letter, we investigate both proc esses. Special emphasis is given to the antiproton signature of supers ymmetric dark matter. The corresponding signal exceeds the conventiona l spallation flux below 300 MeV, a domain that will be thoroughly expl ored by the Antimatter Spectrometer experiment. The propagation of the antiprotons produced in the remote regions of the halo back to the Ea rth plays a crucial role. Depending on the energy, the leaky box estim ates are wrong by a factor varying from 0.5 up to 3.