Hadronic Interaction Studies with the ARGO-YBJ Experiment

Cosmic ray physics in the 10^12- 10^16 eV primary energy range is among the main scientific goals of the ARGO-YBJ experiment. The detector, located at 4300m a.s.l., is a full coverage Extensive Air Shower array consisting of a carpet of Resistive Plate Chambers of about 6700 m^2. The apparatus layout, performance and location offer a unique possibility to make a deep study of several characteristics of the hadronic component of the cosmic ray flux in an energy window marked by the transition from direct to indirect measurements. In this energy region the primary cosmic ray composition is sufficiently well known in order to make unbiased studies on the hadronic interactions. In particular, the proton-air cross section has been measured in the 1-100 TeV energy region and total proton-proton cross section has been estimated at center of mass energies where no accelerator data are currently available. The recently implemented analog readout of the RPC signal allows extending these studies towards higher energies. The lateral distribution of particle density down to few meters from the core and the shower time structure are currently observed with unprecedented resolution, thus giving new tools for the study of hadronic interactions at these energies.