Comparison of Hadronic Interaction Models at Auger Energies

The engineering array of the southern Pierre Auger Observatory (PAO) [3] in Argentina has recently started to take data. The interpretation of the measurements requires reliable numerical simulations of extensive air showers (EAS) in the extremely-high energy (EHE) range > 10 eV. A large uncertainty in such simulations arises from the models which describe the hadronic interactions. As one has to extrapolate in energy from accelerators by several orders of magnitude and into the forward kinematical range which is unobserved by collider experiments, the models have to rely on theoretical guidelines to describe the EHE collisions. In this contribution model predictions for single interactions of p-p, p-N, and π-N collisions are compared, and we examine how their features influence measurable EAS quantities such as the longitudinal development with the shower maximum Xmax and the lateral distributions of particle densities at ground.