ULTRA-HIGH ENERGY COSMIC-RAYS FROM DECAYING RELIC PARTICLES

We report on a recent proposal that particles produced by the decays o f ultraheavy and quasistable X-particles constitute the Ultra High Ene rgy Cosmic Rays (UHE CR). These X-particles are assumed to constitute a tiny fraction xi x of Cold Dark Matter (CDM) in the Universe, with x i x being the same in the halo of our Galaxy and in the intergalactic space. The UHE CR fluxes produced at the decays of X-particles are dom inated by photons and nucleons from the halo of our Galaxy. Thus they do not exhibit the Greisen-Zatsepin-Kuzmin (GZK) cutoff and the cascad e limit is relaxed. We discuss the spectrum of produced Extensive Air Showers (EAS) and a signal from the Virgo cluster as signatures of thi s model.