Constraining superheavy dark matter model of UHECR with SUGAR data

Abstract

Models which associate the origin of the ultra-high energy cosmic rays (UHECR) with decays of relic superheavy dark matter particles (SHDM) predict the anisotropy of UHECR flux toward the Galactic center. We use the existing SUGAR data, which cover the Galactic center, to look for such a signal and limit the fraction of UHECR produced by this mechanism. The absence of anisotropy toward the Galactic center in the SUGAR data implies at 95% confidence level that the fraction of SHDM-related cosmic rays should be less than 20% at E>1×10 19 eV and less than 50% at E>4×10 19 eV. These constraints disfavor at 1−2.5 σ the SHDM decays as explanation of super-GZK events observed by AGASA.