Charge conservation and the shape of the ridge of two-particle correlations in relativistic heavy-ion collisions

TL;DR

This study shows that charge conservation in hydrodynamic models explains the shape and features of two-particle correlations in relativistic heavy-ion collisions, matching experimental data at low transverse momentum.

Contribution

It introduces a detailed hydrodynamic framework incorporating charge conservation to accurately reproduce two-particle correlation data in heavy-ion collisions.

Findings

Charge conservation provides a key non-flow component in correlations.

The model reproduces the dependence of correlations on charge and centrality.

The fall-off of the ridge is explained by particle pairs emitted from the same fluid element.

Abstract

We demonstrate that in the framework of the event-by-event hydrodynamics followed by statistical hadronization, the proper charge conservation in the mechanism of hadron production provides the crucial non-flow component and leads to agreement with the two-dimensional two-particle correlation data in relative azimuthal angle and pseudorapidity at soft transverse momenta (p_T<2GeV). The fall-off of the same-side ridge in relative pseudorapidity follows from the fact that a pair of particles with balanced charges is emitted from the same fluid element, whose collective velocity collimates the momenta of the pair. We reproduce basic experimental features of the two-dimensional correlation function, such as the dependence on the relative charge and centrality, as well as the related charge balance functions and the harmonic flow coefficients as functions of the relative pseudorapidity.