Charged-hadron production in pp, p+Pb, Pb+Pb, and Xe + Xe collisions at √s_NN = 5 TeV with the ATLAS detector at the LHC

This paper presents measurements of charged-hadron spectra obtained in pp, p+Pb, and Pb+Pb collisions at √s or √s_NN = 5.02 TeV, and in Xe+Xe collisions at √s_NN = 5.44 TeV. The data recorded by the ATLAS detector at the LHC have total integrated luminosities of 25 pb⁻¹, 28 nb⁻¹, 0.50 nb⁻¹, and 3 μb⁻¹, respectively. The nuclear modification factors R_pPb and R_AA are obtained by comparing the spectra in heavy-ion and pp collisions in a wide range of charged-particle transverse momenta and pseudorapidity. The nuclear modification factor R_pPb shows a moderate enhancement above unity with a maximum at p_T ≈ 3 GeV; the enhancement is stronger in the Pb-going direction. The nuclear modification factors in both Pb+Pb and Xe+Xe collisions feature a significant, centrality-dependent suppression. They show a similar distinct p_T-dependence with a local maximum at p_T ≈ 2 GeV and a local minimum at p_T ≈ 7 GeV. This dependence is more distinguishable in more central collisions. No significant |η|-dependence is found. A comprehensive comparison with several theoretical predictions is also provided. They typically describe R_AA better in central collisions and in the p_T range from about 10 to 100 GeV.