Charged-particle nuclear modification factors in XeXe collisions at √s_NN = 5.44 TeV

Abstract

The differential yields of charged particles having pseudorapidity within |η| < 1 are measured using xenon-xenon (XeXe) collisions at \(\sqrt{{s}_{NN}}=\phantom{\rule{0.25em}{0ex}}5.44\) TeV. The data, corresponding to an integrated luminosity of 3.42 μb\(^{−1}\), were collected in 2017 by the CMS experiment at the LHC. The yields are reported as functions of collision centrality and transverse momentum, \(p_T\), from 0.5 to 100 GeV. A previously reported \(p_{T}\) spectrum from proton-proton collisions at \(\sqrt{s}=5.02\) TeV is used for comparison after correcting for the difference in center-of-mass energy. The nuclear modification factors using this reference, \(R_{AA}^{*}\), are constructed and compared to previous measurements and theoretical predictions. In head-on collisions, the \(R_{AA}^{*}\) has a value of 0.17 in the \(p_{T}\) range of 6–8 GeV, but increases to approximately 0.7 at 100 GeV. Above ≈6 GeV, the XeXe data show a notably smaller suppression than previous results for lead-lead (PbPb) collisions at \(\sqrt{{s}_{NN}}=5.02\) TeV when compared at the same centrality (i.e., the same fraction of total cross section). However, the XeXe suppression is slightly greater than that for PbPb in events having a similar number of participating nucleons.