Isothermal compressibility of hadronic matter formed in relativistic nuclear collisions

Maitreyee Mukherjee,Sumit Basu,Arghya Chatterjee,Sandeep Chatterjee,Souvik Priyam Adhya,Sanchari Thakur,Tapan K Nayak

doi:10.1016/j.physletb.2018.07.021

Abstract

We present the first estimates of isothermal compressibility (kT) of hadronic matter formed in relativistic nuclear collisions (sNN=7.7 GeV to 2.76 TeV) using experimentally observed quantities. kT is related to the fluctuation in particle multiplicity, temperature, and volume of the system formed in the collisions. Multiplicity fluctuations are obtained from the event-by-event distributions of charged particle multiplicities in narrow centrality bins. The dynamical components of the fluctuations are extracted by removing the contributions to the fluctuations from the number of participating nucleons. From the available experimental data, a constant value of kT has been observed as a function of collision energy. The results are compared with calculations from UrQMD, AMPT, and EPOS event generators, and estimations of kT are made for Pb–Pb collisions at the CERN Large Hadron Collider. A hadron resonance gas (HRG) model has been used to calculate kT as a function of collision energy. Our results show a decrease in kT at low collision energies to sNN∼20 GeV, beyond which the kT values remain almost constant.

Highlights

The determination of the thermodynamic state of matter formed in high-energy nuclear collisions is of great importance in understanding the behaviour of the matter formed at high temperature and/or energy density
Isothermal compressibility is the measure of the relative change in volume with respect to change in pressure [1], kT |T, N
We have studied the isothermal compressibility of the system formed at the√time of chemical freeze-out in relativistic nuclear collisions for sNN from 7.7 GeV to 2.76 TeV

Summary

Introduction

The determination of the thermodynamic state of matter formed in high-energy nuclear collisions is of great importance in understanding the behaviour of the matter formed at high temperature and/or energy density. The experimental data of event-by-event multiplicity fluctuations at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) and Super Proton Synchrotron (SPS) of CERN have been used in combination with temperatures and volumes of the system at the chemical freeze-out to extract the values of kT. These results are compared to that of three event generators and the hadron resonance gas (HRG) model. Our results provide important measures for the beam energy scan program of RHIC and the experiments at the CERN Large Hadron Collider (LHC), and gives guidance for experiments at the Facility for Antiproton and Ion Research (FAIR) at GSI and the Nuclotron-based Ion Collider facility (NICA) at JINR, Dubna

Methodology

Multiplicity fluctuations: experimental data

Multiplicity fluctuations from event generators

Compilation of kT

Findings

Summary