Superheavy dark matter as UHECR source versus the SUGAR data

Decay or annihilation products of superheavy dark matter (SHDM) could be responsible for the end of the Ultra-High Energy Cosmic Ray (UHECR) spectrum. In this case, the south array of the Pierre Auger Observatory should observe in the future a significant anisotropy of UHECR arrival directions towards the galactic center. Here we use the already existing data of the SUGAR array to test this possibility. If decaying SHDM is distributed according a Navarro-Frenk-White (NFW) dark matter profile with core radius Rc = 15 kpc and is responsible only for UHECRs above ∼ 6 × 10 eV, i.e. the AGASA excess, then the arrival directions measured by the SUGAR array have a probability of ∼ 10% to be consistent with this model. By contrast, the model of annihilating SHDM is disfavoured at least at 99% CL by the SUGAR data, if the smooth component of the DM dominates the signal. PACS numbers: 98.70.Sa, 14.80.-j