System-size dependence of charged-particle suppression in ultrarelativistic nucleus-nucleus collisions

High-energy partons lose energy while propagating through the hot, strongly interacting medium produced in ultrarelativistic nucleus-nucleus collisions, leading to a suppression of particle production at high transverse momentum (p _T). The dependence of this energy loss on the size of the colliding nuclear system has yet to be firmly established experimentally. This Letter presents a systematic study of charged-particle suppression across four different nucleus-nucleus collision systems using nuclear modification factors (R _AA) measured by the CMS Collaboration at the CERN LHC. Previous CMS measurements of R _AA in oxygen-oxygen, xenon-xenon, and lead-lead collisions are recast with identical p _T intervals and are complemented by the first measurement of the charged-particle R _AA in neon-neon collisions at [b]s_NN=5.36TeV. The neon-neon data correspond to an integrated luminosity of 0.76nb⁻¹. The R _AA in all collision systems examined show similar qualitative trends as a function of p _T, but have a magnitude which is ordered with the nucleon number A . The R _AA feature a downward slope at low p _T, a local minimum at around 5–7GeV, and an upward slope with increasing p _T. The R _AA are also compared in terms of A ^1/3, which is proportional to the nuclear radius. Models including only initial-state nuclear effects fail to reproduce the observed trends, whereas energy loss models reproduce the trends in the region p_T'9.6GeV.