Anisotropies of Cosmic Rays and Search for Intergalactic Cascades from the direction of the Highest Energetic Cosmic Ray Events with the HEGRA Scintillator Array

Abstract

Data taken with the HEGRA Scintillator Array have been used to search for spatial anisotropies in the arrival directions of cosmic rays above 20 TeV. In this paper results on the search for TeV gamma-ray emission from the Galactic plane and the Gould belt are presented. Furthermore, a search for TeV gamma-ray emission correlated with the arrival directions of cosmic rays with energies well beyond the Greizen-Zatsepin-Kuzmin cutoff has been performed. Such a correlation can be expected from sufficiently high energetic nuclei inducing electromagnetic cascades on the diffuse intergalactic background radiation, eventually producing TeV photons. Interestingly, the direction of the most energetic event yields the highest excess with a chance probability of 1.8%.