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 s NN = 9.62 TeV center-of-mass energy with the ATLAS detector, corresponding to 634 μ b − 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 . p O = 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.