Multiplicity and transverse momentum evolution of charge-dependent correlations in pp, p-Pb, and Pb-Pb collisions at the LHC

Adam, J. and Adamova, D. and Aggarwal, M. M. and Rinella, G. A. and Agnello, M. and Barnaföldi, Gergely Gábor and Bencédi, Gyula and Berényi, Dániel and Boldizsár, László and Dénes, Ervin and Hamar, Gergő and Kiss, Gábor and Varga-Kőfaragó, Mónika and Lévai, Péter and Oláh, László and Pochybova, Sona (2016) Multiplicity and transverse momentum evolution of charge-dependent correlations in pp, p-Pb, and Pb-Pb collisions at the LHC. EUROPEAN PHYSICAL JOURNAL C, 76 (2). ISSN 1434-6044

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Abstract

We report on two-particle charge-dependent correlations in pp, p–Pb, and Pb–Pb collisions as a func- tion of the pseudorapidity and azimuthal angle difference, ∆ η and ∆ ϕ respectively. These correla- tions are studied using the balance function that probes the charge creation time and the development of collectivity in the produced system. The dependence of the balance function on the event multi- plicity as well as on the trigger and associated particle transverse momentum (pT) in pp, p-Pb, and Pb–Pb collisions at √sNN = 7, 5.02, and 2.76 TeV, respectively, are presented. In the low transverse momentum region, for 0.2 < pT < 2.0 GeV/c, the balance function becomes narrower in both ∆ η and ∆ ϕ directions in all three systems for events with higher multiplicity. The experimental findings favor models that either incorporate some collective behavior (e.g. AMPT) or different mechanisms that lead to effects that resemble collective behavior (e.g. PYTHIA8 with color reconnection). For higher values of transverse momenta the balance function becomes even narrower but exhibits no multiplicity dependence, indicating that the observed narrowing with increasing multiplicity at low pT is a feature of bulk particle production.

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