Mass composition and cross-section from the shape of cosmic ray shower longitudinal profiles

The longitudinal development of extreme energy cosmic ray showers has a characteristic “Universal Shower Profile” when normalized and translated to the shower maximum. Experimentally accessible observables can be defined to parametrize the average shape and characterize each event. By describing the full shape of the profile, information related to the first hadronic interactions and primary particle type can be extracted. A shape variable which measures the distance from the first interaction to the depth of maximum can lead to a cosmic ray composition analysis with independent extraction of the primary cross-sections.