Measurement of Charged-Particle Production in sqrt[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[s_{NN}]=9.62  TeV center-of-mass energy with the ATLAS detector, corresponding to 634  μb^{-1} of integrated luminosity. A total of 246×10^{6} selected events have at least one track with transverse momentum p_{T}>500  MeV and pseudorapidity |η|<2.5. The measured fiducial proton-oxygen cross section is σ_{fid.}^{pO}=396±6(exp.)±9(lumi.)  mb and the extrapolated inelastic proton-air cross section is σ_{inel.}^{p+air}=406±6(exp.)±9(lumi.)±28(th.)  mb. Measurements of charged-particle multiplicity, p_{T}, 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.