A joint INT/Bartol workshop at the Institute for Nuclear Theory -- Nuclear Interactions at Ultra-high Energy in Light of Recent Results from Auger

February 20-22, 2008

The Auger Observatory has recently identified an association between the highest energy cosmic rays and nearby Active Galactic Nuclei (AGN), which is best interpreted if the cosmic rays are protons. Both Auger and HiRes have measured the depth of shower maximum (Xmax) as a function of energy from below 1 EeV to approaching 100 EeV. Implications of the Xmax measurements are still not clear, but some interpretations require a large fraction of heavy nuclei.

Interpretation of shower characteristics that allow one to infer composition of the primary nuclei depend critically on models of hadronic interactions used to interpret the measurements. Extrapolations of several orders of magnitude beyond accelerator energies are required, and nuclear effects may be important.

The recent Auger results (Science, November 9, 2007) highlights the need for an improved understanding of hadronic interaction models at ultra-high energy, up to 300 TeV equivalent center of mass energy. The purpose of this workshop is to bring together a limited number (<40) of nuclear, particle and cosmic-ray physicists to clarify the existing situation and lay the groundwork for a better understanding of interactions of nuclei at ultra-high energy.

Updated: February 12, 2008