Method to Look for Imprints of Ultrahigh Energy Nuclei Sources

Abstract

We propose a new method to search for heavy nuclei sources, on top of background, in the Ultra-High Energy Cosmic Ray data. We apply this method to the 69 events recently published by the Pierre Auger Collaboration and find a tail of events for which it reconstructs the source at a few degrees from the Virgo galaxy cluster. The reconstructed source is located at ~ 8.5 degrees from M87. The probability to have such a cluster of events in some random background and reconstruct the source position in any direction of the sky is about 7 x 10^(-3). The probability to reconstruct the source at less than 10 degrees from M87 in a data set already containing such a cluster of events is about 4 x 10^(-3). This may be a hint at the Virgo cluster as a bright ultra-high energy nuclei source. We investigate the ability of current and future experiments to validate or rule out this possibility, and discuss several alternative solutions which could explain the existing anisotropy in the Auger data.