2024

The CMS collaboration; Tumasyan, A.; Adam, W.; Eerola, P.; Forthomme, Laurent; Kirschenmann, H.; Österberg, K.; Voutilainen, M.; Bharthuar, Shudhashil; Brücken, Erik; Garcia, F.; Havukainen, J.; Heikkilä, Jaana; Kim, Minsuk; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.

Measurements of the charge-dependent two-particle angular correlation function in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 8.16 TeV and lead-lead (PbPb) collisions at $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5.02 TeV are reported. The pPb and PbPb data sets correspond to integrated luminosities of 186 nb-1 and 0.607 nb-1, respectively, and were collected using the CMS detector at the CERN LHC. The charge-dependent correlations are characterized by balance functions of same- and opposite-sign particle pairs. The balance functions, which contain information about the creation time of charged particle pairs and the development of collectivity, are studied as functions of relative pseudorapidity (??) and relative azimuthal angle (??), for various multiplicity and transverse momentum (pT) intervals. A multiplicity dependence of the balance function is observed in ?? and ?? for both systems. The width of the balance functions decreases towards high-multiplicity collisions in the momentum region