Toward a description of the centrality dependence of the charge balance function in the HYDJET++ model

TL;DR

This paper analyzes the charge balance function in Pb+Pb collisions at the LHC using the HYDJET++ model, highlighting the importance of charge conservation mechanisms and their impact on the centrality dependence of the balance function.

Contribution

It introduces a method to incorporate exact charge conservation into the thermal model without altering other parameters, improving the description of experimental data.

Findings

The model qualitatively reproduces the centrality dependence of the balance function widths.

Including exact charge conservation via the canonical ensemble improves the model's accuracy.

At higher transverse momenta, charge correlations are dominated by jet contributions.

Abstract

Data from the Large Hadron Collider on the charge balance function in Pb+Pb collisions at center-of-mass energy 2.76~TeV per nucleon pair are analyzed and interpreted within the framework of the \hydjet++ model. This model allows us to qualitatively reproduce the experimentally observed centrality dependence of the balance function widths at relatively low transverse momentum intervals due to the different charge creation mechanisms in soft and hard processes. However, a fully adequate description of the balance function in these intervals implies an essential modification of the model by including exact charge conservation via the canonical rather than the grand canonical ensemble. A procedure is proposed for introducing charge correlations into the thermal model without changing other model parameters. With increasing transverse momenta, the default model results describe the experimental data much better because the contribution of the soft component of the model is significantly reduced in these transverse momentum intervals. In practical terms, there is a transition to a single source of charge correlations, namely, charge correlations in jets in which exact charge conservation holds at each stage.