Constraints on string percolation model from anomalous centrality evolution data in Au-Au collisions at $\mathbf{\sqrt{s_{NN}}=}$ 62 and 200 GeV

TL;DR

This paper investigates how string percolation models can explain the anomalous centrality evolution and ridge structures in Au-Au collisions at RHIC energies, and extrapolates findings to LHC energies, linking string interactions to flow phenomena.

Contribution

It introduces constraints on the string percolation model based on centrality data and explores string interactions' role in collective flow and ridge formation at high energies.

Findings

Constraints on string percolation model from centrality data

High string densities confirmed at LHC energies

String interactions can explain flow phenomena

Abstract

Anomalous centrality evolution of two-particle angular correlations observed in Au-Au collisions at $\sqrt{s_{NN}} = 62$ and 200 GeV and the onset of ridge structures are considered in the model of interacting quark-gluon strings. We assume that at the given energy of nucleus-nucleus collisions the critical energy density may be reached at the specific centrality. In a string percolation model this might be treated equivalently to a formation of a large cluster of strings characterized by the critical string density, with a size comparable to the whole area of interaction of two nuclei. This hypothesis allows to define some constraints on the string percolation model using data on transitional centralities in Au-Au collisions at these two energies. Results are extrapolated to the LHC energy where high string densities (exceeding the critical value) are confirmed for all classes of centralities in Pb-Pb collisions. Interaction between strings inside large clusters formed in nucleus-nucleus collisions is considered in a simplified Monte Carlo model. This model is applied to the qualitative analysis of the onset of collectivity and the ridge formation in Pb-Pb collisions. It is shown that the approach of the repulsive string-string interaction is capable to explain the appearance of elliptic and triangular flow observed in nucleus-nucleus collisions at RHIC and LHC energies.