Dependence of Temperatures and Kinetic Freeze-Out Volume on Centrality in Au-Au and Pb-Pb Collisions at High Energy

Muhammad Waqas,Zafar Wazir,Fu-Hu Liu

doi:10.1155/2020/8198126

Abstract

Centrality-dependent double-differential transverse momentum spectra of negatively charged particles (π−, K−, and p¯) at the mid(pseudo)rapidity interval in nuclear collisions are analyzed by the standard distribution in terms of multicomponent. The experimental data measured in gold-gold (Au-Au) collisions by the PHENIX Collaboration at the Relativistic Heavy Ion Collider (RHIC) and in lead-lead (Pb-Pb) collisions by the ALICE Collaboration at the Large Hadron Collider (LHC) are studied. The effective temperature, initial temperature, kinetic freeze-out temperature, transverse flow velocity, and kinetic freeze-out volume are extracted from the fitting to transverse momentum spectra. We observed that the mentioned five quantities increase with the increase of event centrality due to the fact that the average transverse momentum increases with the increase of event centrality. This renders that larger momentum (energy) transfer and further multiple scattering had happened in central centrality.

Highlights

One of the most important questions in high-energy collisions is the identification of various phases of dense matter
Within the framework of statistical thermal models, it is assumed that the initial stage of collisions of nuclei at the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) [9,10,11] gives a tremendous amount of temperature, where a hot and dense “fireball” over an extended region for a very short period of time is formed
One can see the wellapproximate description of the model results to the experimental data of the PHENIX Collaboration in special pT ranges in high-energy Au-Au collisions at the RHIC

Summary

Introduction

One of the most important questions in high-energy collisions is the identification of various phases of dense matter. It is expected to reach a deconfined state of matter (quarks and gluons) at high energy or density. This state of matter is called Quark-Gluon Plasma (QGP), which was obtained in the early universe shortly after the big bang prior to the condensation in hadrons. After the hadronization of the fireball, the hadrons continuously interact with each other and the particle number changes. This process results in a decrease of temperature and at a certain value where the reaction process stops and the temperature at this point is called the “chemical freeze-out temperature” (Tch). At the stage of chemical freeze-out, the yield ratios of different types of particles remain invariant [13]

Methods

Results

Conclusion