Proton-air cross section measurement with the ARGO-YBJ cosmic ray experiment

The proton-air cross section in the energy range 1-100 TeV has been measured by the ARGO-YBJ cosmic rayexperiment. The analysis is based on the primary cosmic rayflux attenuation for different atmospheric depths (i.e. zenithangles) and exploits the detector capabilities of selecting the showerdevelopment stage by means of hit multiplicity, density and lateral profile measurements at ground. The effects of showerfluctuations, the contribution of heavier primaries and the uncertainties of the hadronic interaction models, have been taken into account. The results have been used to estimate the total proton-proton cross section at center-of- massenergies between 70 and 500 GeV, where no accelerator data are currently available.