Ultra-high--energy Cosmic Ray Astronomy and Astrophysics with the Pierre Auger Observatory

Ultra-high--enegry cosmic rays are the most energetic particles in the Universe. These particles cannot reach the surface of the Earth: they interact with the Earth's atmosphere, and produce secondary particle air-showers.

The Pierre Auger Observatory detects the signatures of these air showers, through telescopes looking for the fluorescence emission from the atmosphere in response to the shower, and through a vast surface array of tanks filled with water, looking for the for the Cerenkov emission of the secondary particles when they reach the ground and propagate in the tank water. From these signatures, the arrival direction and energy of each particle can be reconstructed.

Pierre Auger observations of ultra-high--energy cosmic rays will help answer long-standing questions on the energy spectrum, the composition, and, ultimately, the sources of these highest-energy particles. Recently, The Pierre Auger collaboration announced that the highes-energy cosmic-ray sky appears to be anisotropic, with a statistical significance of the measured deviation from isotropy better than 1% in an a priori defined statistical test (access the Science letter here and a longer, more deltailed description of the statistical analysis here).

Members of the Chicago Auger group have been actively working on better understanding this anisotropy signal, and evaluate its potential to point us directly to the sources of ultra-high--energy cosmic rays. Our contributions towards this direction can be accessed here (Auger password required for full text).

Recent refereed Pierre Auger collaboration publications can be found here.