Search for clustering of ultra high energy cosmic rays from the Pierre Auger Observatory

Abstract

We present the results of a search for clustering among the highest energy events detected by the surface detector of the Pierre Auger Observatory between 1 January 2004 and 31 August 2007. We analyse the autocorrelation function, in which the number of pairs with angular separation within a given angle is compared with the expectation from an isotropic distribution. Performing a scan in energy above 30 EeV and in angles smaller than 30 degrees, the most significant excess of pairs appears for E > 57 EeV and for a wide range of separation angles, between 9 and 22 degrees. An excess like this has a chance probability of about 2% to arise from an isotropic distribution and appears at the same energy threshold at which the Pierre Auger Observatory has reported a correlation of the arrival directions of cosmic rays with nearby astrophysical objects.

Contribution to the Proceedings of the CRIS 2008 Conference

References in corpus (3)

• Observation of the suppression of the flux of cosmic rays above 4x10^19eV
• First hints of large scale structures in the ultra-high energy sky?
• Astrophysical interpretation of the medium scale clustering in the ultra-high energy sky

Cited by in corpus (5)

• Superbradyons and some possible dark matter signatures
• Preon models, relativity, quantum mechanics and cosmology (I)
• The correlation of UHECRs with nearby galaxies in the Local Volume
• Extended clustering analyses to constrain the deflection angular scale and source density of the ultra-high-energy cosmic rays
• Techniques to study cosmic ray anisotropies