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 ray experiment. The analysis is based on the primary cosmic ray flux attenuation for different atmospheric depths (i.e. zenith angles) and exploits the detector capabilities of selecting the shower development stage by means of hit multiplicity, density and lateral profile measurements at ground. The effects of shower fluctuations, 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-mass energies between 70 and 500 GeV, where no accelerator data are currently available.