On Pseudorapidity Distribution and Speed of Sound in High Energy Heavy Ion Collisions Based on a New Revised Landau Hydrodynamic Model

Li-Na Gao,Fu-Hu Liu

doi:10.1155/2015/184713

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. The modeling results are in agreement with the available experimental data at relativistic heavy ion collider, large hadron collider, 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 energies of the two colliders, the central source undergoes a phase transition from hadronic gas to quark-gluon plasma liquid phase; meanwhile, the target/projectile sources remain in the state of hadronic gas. The present work confirms that the quark-gluon plasma is of liquid type rather than being of a gas type.

Highlights

In fields of particle physics and nuclear physics, heavy ion collisions at high energies are a very important research subject
We propose a new revision on the Landau hydrodynamic model based on the three-source picture to describe systematically the pseudorapidity distributions of charged particles produced in Au-Au, Cu-Cu, Pb-Pb, d-Au, Au-Em, and p-Em collisions at high energies
We studied the square speed of sound parameter in our previous work [36, 37], the physics picture and calculation method used there are different from the present work

Summary

Introduction

In fields of particle physics and nuclear physics, heavy ion (nucleus-nucleus) collisions at high energies are a very important research subject. In fixed target experiments as well (such as in nuclear emulsion experiments at high energies), proton to gold induced emulsion (p-Em and Au-Em) collisions have presented pseudorapidity distributions with abundant structures [27,28,29]. More other ions such as helium, carbon, oxygen, neon, silicon, sulphur, and krypton have been used [30, 31]. We propose a new revision on the Landau hydrodynamic model based on the three-source picture to describe systematically the pseudorapidity distributions of charged particles produced in Au-Au, Cu-Cu, Pb-Pb, d-Au, Au-Em, and p-Em collisions at high energies. Based on the descriptions of pseudorapidity distributions, the values of square speed of sound parameter are extracted from the widths of rapidity distributions

The Model and Calculation Method

Comparisons with Experimental Data

Discussions

Conclusions