Measurement of charged-particle production in $\sqrt{s_\text{NN}}=9.62$ TeV proton-oxygen collisions as a probe of cosmic-ray air showers with the ATLAS detector

Abstract

This Letter presents a measurement of prompt charged-particle production in proton-oxygen interactions at $\sqrt{s_\text{NN}}=9.62$ TeV center-of-mass energy with the ATLAS detector, corresponding to 634 $\mu$b$^{-1}$ of integrated luminosity. A total of 246 million selected events have at least one track with transverse momentum $p_\text{T}> 500$ MeV and pseudorapidity $|\eta|<2.5$. The measured fiducial proton-oxygen cross section is $\sigma_\text{fid.}^{p\text{O}}=396 \pm 6~(\text{exp.}) \pm 9~(\text{lumi.})~\text{mb}$ and the extrapolated inelastic proton-air cross section is $\sigma^{p+\text{air}}_\text{inel.} = 406 \pm 6~(\text{exp.}) \pm 9~(\text{lumi.}) \pm 28~(\text{th.})~\text{mb}$. Measurements of charged-particle multiplicity, $p_\text{T}$, and $\eta$ 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.