Charged-particle nuclear modification factors in XeXe collisions at $ \sqrt{s_{\mathrm{NN}}} = 5.44 $ TeV

The differential yields of charged particles having pseudorapidity within |η| < 1 are measured using xenon-xenon (XeXe) collisions at $\sqrt{s_{\mathrm{NN}}} = 5.44$ 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 $\sqrt{s_{\mathrm{NN}}}=5.02$ 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.