Search

The Pierre Auger Observatory has been designed to investigate the origin and the nature of Ultra High Energy Cosmic Rays using a hybrid detection technique. It is located in the Province of Mendoza, Argentina, and consists of a surface array of about 3000 km2 overlooked by 27 air fluorescence telescopes grouped in four sites, which together provide a powerful instrument for air shower reconstruction. The combination of information from the surface array, measuring the lateral distributions of secondary particles at the ground, and the fluorescence telescopes, observing the longitudinal profile, enhances the reconstruction capability with respect to the individual detector components. Ultra High Energy Cosmic Rays offer also the unique chance of investigating particle interactions over an energy range well beyond the one covered by present and future ground-based particle accelerators. A review of selected results is presented with the emphasis given to the measurement of energy spectrum, arrival directions, chemical composition and the search for photons and neutrinos as primary particles. [ABSTRACT FROM AUTHOR]

The observation of cosmic ray air showers above 10[sup 20] eV poses three serious challenges for particle astrophysics: (i) how the primary particles are accelerated to these fantastic multi-Joule energies, (ii) how the primaries evade energy loss while crossing a Universe filled with radiation, and (iii) why events appear to cluster in direction. The data is briefly reviewed. Then some novel solutions to these problems, generally involving new physics, are explored. Emphasis is placed on the signatures by which cosmic ray experiments will discriminate among proposed solutions, and the role neutrinos may play in resolving puzzles. [ABSTRACT FROM AUTHOR]

The role of Horizontal Showers induced by cosmic rays is discussed in detail. A new approach to the calculation of the muon component in horizontal air showers induced by protons, heavier nuclei or photons is presented which allows a simple analytical evaluation of the muon density profiles at ground level. The results of the first application of these results to horizontal air showers detected at the Haverah Park Array by the recently started Leeds-Santiago collaboration, leading to important restrictions on composition at ultra high energies, are reported. [ABSTRACT FROM AUTHOR]