Probing Proton Cross Sections with Cosmic Rays

The Pierre Auger Observatory measures the longitudinal air shower profile of ultra high energy cosmic rays which gives information on composition and hadronic interaction properties. Eun-Joo Ahn and colleagues use this data to obtain the proton-air cross section. Preliminary results show a surprising rise in the cross section with energy, which is not predicted by current hadronic interaction models. This is a hint of new physics at energies inaccessible to the LHC. More data from Auger is expected to resolve the issue.

– Eun-joo Ahn