Dark matter halos and the anisotropy of ultra-high energy cosmic rays

Several explanations for the existence of Ultra-High Energy Cosmic Rays inv oke the idea that they originate from the decay of massive particles create d in the reheating following inflation. It has been suggested that the deca y products can explain the observed isotropic flux of cosmic rays. We have calculated the anisotropy expected for various models of the dark matter di stribution and find that at present data are too sparse above 4 x 10(19) eV to discriminate between different models. However, we show that with data from three years of operation of the southern section of the Pierre Auger O bservatory significant progress in testing the proposals will be made. (C) 1999 Elsevier Science B.V. All rights reserved.