Proton-proton Cross Section at sqrt(s) \sim 30 TeV
  There are both theoretical and experimental uncertainties in using data from cosmic-ray air showers to estimate hadronic cross sections above accelerator energies. We outline these problems and compare the physics used to extract \sigma_{pp}^{tot} from air shower data to the widely used parameterization of the proton-proton cross section of Donnachie and Landshoff and other contemporary models. We conclude that the published cosmic-ray cross section values do not strongly constrain \sigma_{pp}^{tot} fits from lower energy accelerator data. 
Ralph Engel (1), T.K. Gaisser (1), Paolo Lipari (2) and Todor Stanev   (1) ((1) Bartol Research Institute, Newark, USA (2) D...