Extensive Air Showers as probes of hadronic interactions beyond the LHC energies

Above 1 PeV, the properties of cosmic rays can only be inferred indirectly through the detection of extensive air showers. The interpretation of air shower observables at 10 EeV relies on extrapolations of accelerator data by about one order of magnitude in energy, where a proper description of the very forward physics, most relevant for the shower development, is lacking. This leads to unknown systematic uncertainties in the predictions of hadronic interaction models and inconsistencies in the description of air shower data. We aim at improving the current situation through a comprehensive study of the main shower observables (lateral and longitudinal profiles of muon and electromagnetic components) and of the properties of current hadronic interaction models using data of several air shower experiments. The analysis will be based on several popular simulation codes and will include an unprecedented wide scan on the hadronic parameters (cross-section, multiplicity, elasticity, pion-charge ratio) placing constraints on the hadronic interaction models and exotic physics scenarios.