Super high energy cosmic ray events and properties of hadronic interactions

This review summarizes the results from large scale emulsion chamber experiments carried out to study super high energy interactions using the cosmic ray beam. These events have a total visible energy greater than 100 TeV or a center of mass energy greater than 700 GeV. Over 1000 events have been observed at mountain laboratories around the world. These experiments provide evidence for continued increase of QCD jet production above SPS PP collider energies, a possible breakdown of scaling in the fragmentation region and a continuing increase in the total cross section. In addition, the results strongly suggest a dominance of nuclei with atomic mass between 20≤A≤56 in the primary cosmic ray beam at 106−107 GeV per nucleus, in the region of the ‘bend’ of the all‐particle cosmic ray spectrum.