Large- and Medium-scale Anisotropies in the Arrival Directions of Cosmic Rays Observed with KASCADE-Grande

We search for anisotropies in the arrival directions of cosmic rays (CRs) observed by the KASCADE-Grande air shower experiment. The analysis is based on public data of about 23.7 million events with reconstructed primary energies above 1 PeV. We apply a novel maximum-likelihood reconstruction method for the CR anisotropy that compensates for spurious anisotropies induced by local detector effects. We find no evidence for a large-scale dipole anisotropy in the data, consistent with official results based on the conventional east–west derivative method. On the other hand, a subset of CRs with a median energy of 33 PeV shows strong evidence for a medium-scale feature with an angular diameter of 40°. After accounting for the look-elsewhere effect, the post-trial significance of this medium-scale feature is at the level of 4σ.