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

Data taken with the HEGRA Scintillator Array within 2.5 years have been used to search for spatial anisotropies in the arrival directions of cosmic rays (E > 20 TeV). For this purpose partial sky survey maps are produced, carefully taking the detector response and changing conditions in the atmosphere into account. In this paper, results on the search for TeV –emission correlated with the Galactic Plane and the Gould Belt, a local Galactic region with an enhanced concentration of young bright stars, molecular and dust clouds, are presented. The upper limit for the emission from the Galactic disc of = CR 10 4 for jbgj 5 (bg denoting the Galactic latitude) and E > 42 TeV imposes constraints on the extrapolation of the -ray flux measured by EGRET. Furthermore, a search for extended TeV –emission correlated with the arrival directions of the cosmic rays with energies well beyond the Greisen-Zatsepin-Kuzmin cutoff has been performed. For this purpose, the directions of 10 events with energies beyond 5 10 eV including the events belonging to three AGASA clusters and the most energetic event (E = 320 EeV) detected by the Fly’s eye detector have been examined for correlated TeV emission. Such a correlation can be expected from sufficiently high energetic nuclei inducing electromagnetic cascades on the diffuse intergalactic (2.7 K) 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%.