On pseudorapidity distribution and speed of sound in high energy heavy ion collisions based on a new revised Landau hydrodynamic model

TL;DR

This paper introduces a revised Landau hydrodynamic model to analyze pseudorapidity distributions in high-energy heavy ion collisions, revealing the phase transition to quark-gluon plasma and confirming its liquid nature.

Contribution

A new revised Landau hydrodynamic model is developed to systematically study pseudorapidity distributions across a wide energy range, incorporating multiple sources and phase transition analysis.

Findings

Model agrees with experimental data from RHIC and LHC.

Central source undergoes a phase transition to QGP liquid.

Participants mostly in a QGP liquid phase with minor hadronic gas presence.

Abstract

We propose a new revised Landau hydrodynamic model to study systematically the pseudorapidity distributions of charged particles produced in heavy ion collisions over an energy range from a few GeV to a few TeV per nucleon pair. The interacting system is divided into three sources namely the central, target, and projectile sources respectively. The large central source is described by the Landau hydrodynamic model and further revised by the contributions of the small target/projectile sources. In the calculation, to avoid the errors caused by an unapt conversion or non-division, the rapidity and pseudorapidity distributions are obtained respectively. The modeling results are in agreement with the available experimental data at relativistic heavy ion collider (RHIC), large hadron collider (LHC), and other energies for different centralities. The value of square speed of sound parameter in different collisions has been extracted by us from the widths of rapidity distributions. Our results show that, in heavy ion collisions at RHIC and LHC energies, the central source undergoes through a phase transition from hadronic gas to quark-gluon plasma (QGP) liquid phase; meanwhile, the target/projectile sources remain in the state of hadronic gas. The present work confirms that the QGP is of liquid type rather than that of a gas. The whole region of participants undergoes through a mixed phase consisting of a large quantity of (>90%) QGP liquid and a small quantity of (<10%) hadronic gas.