Revisiting the centrality definition and observable centrality dependence of relativistic heavy-ion collisions in PACIAE model

TL;DR

This paper refines the impact parameter definition in the PACIAE model for relativistic heavy-ion collisions, aligning it with experimental observations, and updates the simulation code to improve modeling of nuclear collisions, achieving good agreement with experimental data.

Contribution

The paper introduces an improved impact parameter definition in PACIAE, updates the code to version 2.2.2 for unified collision studies, and validates the model against experimental data.

Findings

Impact parameter extension to 20 fm aligns with experimental reports.

PACIAE 2.2.2 reproduces charged-particle distributions accurately.

Model results are consistent with MC-Glauber calculations within error bars.

Abstract

We improve the centrality definition in impact parameter in PACIAE model responding the fact reported by the ALICE, ATLAS, and CMS collaborations that the maximum impact parameter in heavy ion collisions should be extended to 20 $fm$. Meanwhile the PACIAE program is updated to a new version of PACIAE 2.2.2 with convenience of studying the elementary nuclear collisions, proton-nucleus collisions, and the nucleus-nucleus collisions in one unified program version. The new impact parameter definition together with the optical Glauber model calculated impact parameter bin, $N_{part}$, and $N_{coll}$ in proton-nucleus and nucleus-nucleus collisions at relativistic energies are consistent with the improved MC-Glauber model ones within the error bar. The charged-particle pseudorapidity and the transverse momentum distributions in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV simulated by PACIAE 2.2.2 well reproduce the ALICE experimental data.