Multiplicity and transverse momentum dependence of charge-balance functions in pPb and PbPb collisions at LHC energies

Abstract

Measurements of the charge-dependent two-particle angular correlation function in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}$ = 8.16 TeV and lead-lead (PbPb) collisions at $\sqrt{s_{\mathrm{NN}}}$ = 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 ($\Delta \eta$) and relative azimuthal angle ($\Delta \varphi$), for various multiplicity and transverse momentum ($p_{\mathrm{T}}$) intervals. A multiplicity dependence of the balance function is observed in $\Delta \eta$ and $\Delta \varphi$ for both systems. The width of the balance functions decreases toward high-multiplicity collisions in the momentum region $<$ 2 GeV, for pPb and PbPb results. Integrals of the balance functions are presented in both systems, and a mild dependence of the charge-balancing fractions on multiplicity is observed. No multiplicity dependence is observed at higher transverse momentum. The data are compared with HYDJET, HIJING and AMPT generator predictions, none of which capture completely the multiplicity dependence seen in the data. The comparison of results with different center-of-mass energies suggest that the balance functions become narrower at higher energies, which is consistent with the idea of delayed hadronization and the effect of radial flow.

Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-21-017 (CMS Public Pages)

References in corpus (5)

• Description and performance of track and primary-vertex reconstruction with the CMS tracker
• Heavy ion event generator HYDJET++ (HYDrodynamics plus JETs)
• On the Origin of the "Ridge" phenomenon induced by Jets in Heavy Ion Collisions
• Evolving Charge Correlations in a Hybrid Model with both Hydrodynamics and Hadronic Boltzmann Descriptions
• Charge Balance Functions for Heavy-Ion Collisions at LHC Energies

Cited by in corpus (3)

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• Two-particle number and transverse momentum balance function with event topology in pp collisions at $\sqrt{s}=13$ TeV
• System size and event shape dependence of particle-identified balance functions in proton-proton collisions at $\sqrt{s}=13$ TeV using PYTHIA 8 and EPOS models