Measurement of Charged-Particle Production in s NN = 9.62 TeV Proton-Oxygen Collisions as a Probe of Cosmic-Ray Air Showers with the ATLAS Detector

This Letter presents a measurement of prompt charged-particle production in proton-oxygen interactions at sqrt[sNN]=9.62 TeV center-of-mass energy with the ATLAS detector, corresponding to 634 μb⁻¹ of integrated luminosity. A total of 246×10⁶ selected events have at least one track with transverse momentum pT>500 MeV and pseudorapidity |η|<2.5. The measured fiducial proton-oxygen cross section is σfid.pO=396±6(exp.)±9(lumi.) mb and the extrapolated inelastic proton-air cross section is σinel.ᵖ⁺ᵃⁱʳ=406±6(exp.)±9(lumi.)±28(th.) mb. Measurements of charged-particle multiplicity, pT, and η distributions are an order-of-magnitude more precise than differences between hadronic-interaction models. These results enable improved modeling of cosmic-ray air showers, which is important for astroparticle physics.