Search for energy-position correlated multiplets in the data of the Pierre Auger Observatory

Full text: The identification of sources of ultra-high-energy cosmic rays has been a challenge over the last decades. Finding possible sources is complicated by the deflections that cosmic rays suffer when traversing the intervening magnetic fields in the propagation from their sources to Earth. These deflections are expected to be inversely proportional to the energy of the cosmic rays. We present the results of a search for groups of directionally- aligned events recorded by the Pierre Auger Observatory, exhibiting strong correlation between arrival directions and the inverse of their energies. Such a signature is foreseen for sets of events coming from a same source after having been deflected by a coherent magnetic field. A search for energy-position correlated multiplets in the data above 20 EeV has been performed. The largest multiplets found are one 12-plet and two independent decuplets. The positions of the potential sources in the sky are reconstructed for the observed multiplets and the deflection power of the eventual sources is also estimated. Given that the probability of such formations appearing by chance from an isotropic distribution of events is 6% for the 12-plet and 20% for at least three multiplets with ten or more events, there is still no significant evidence for the presence of multiplets arising from magnetic deflection in the data so far. Future data of the Pierre Auger Observatory will allow to check whether the observed multiplets grow significantly and if new multiplets appear. (author)