Analyzing Transverse Momentum Spectra of Pions, Kaons and Protons in p-p, p-A and A-A Collisions via the Blast-Wave Model with Fluctuations.

Hai-Ling Lao,Bo-Qiang Ma,Fu-Hu Liu

doi:10.3390/e23070803

Abstract

The transverse momentum spectra of different types of particles, , , p and , produced at mid-(pseudo)rapidity in different centrality lead–lead (Pb–Pb) collisions at 2.76 TeV; proton–lead (p–Pb) collisions at 5.02 TeV; xenon–xenon (Xe–Xe) collisions at 5.44 TeV; and proton–proton (p–p) collisions at 0.9, 2.76, 5.02, 7 and 13 TeV, were analyzed by the blast-wave model with fluctuations. With the experimental data measured by the ALICE and CMS Collaborations at the Large Hadron Collider (LHC), the kinetic freeze-out temperature, transverse flow velocity and proper time were extracted from fitting the transverse momentum spectra. In nucleus–nucleus (A–A) and proton–nucleus (p–A) collisions, the three parameters decrease with the decrease of event centrality from central to peripheral, indicating higher degrees of excitation, quicker expansion velocities and longer evolution times for central collisions. In p–p collisions, the kinetic freeze-out temperature is nearly invariant with the increase of energy, though the transverse flow velocity and proper time increase slightly, in the considered energy range.

Highlights

In high-energy collisions, one of the most important questions is the identification of various phases of dense matter
The symbols represent the experimental data measured by the ALICE Collaboration in different centralities [29] and the curves are our fitting results by using the blast-wave model with fluctuations, i.e., Equation (4)
One can see the good approximate descriptions of the model results for the experimental data of the ALICE Collaboration in the pT√spectra of the identified particles produced in different centralities for Pb–Pb collisions at sNN = 2.76 TeV

Summary

Introduction

In high-energy collisions, one of the most important questions is the identification of various phases of dense matter. Kinetic freeze-out temperature, transverse flow velocity and proper time are three important parameters with which to characterize the thermal properties of different stages during high-energy p–p, proton–nucleus (p–A) and nucleus–nucleus (A–A) collisions. The kinetic freeze-out temperature describes the excitation degree of the interacting system at the stage of kinetic and thermal equilibrium in which the (transverse) momentum spectra of particles are no longer changed. By inheritance and through development, the blast-wave model with fluctuations can extract the kinetic freeze-out temperature, transverse flow velocity and proper time simultaneously. To understand the thermal properties of different stages of high energy collisions, we applied the blast-wave model with fluctuations to study the transverse momentum (pT) spectra of different particles produced in A–A, p–A and p–p collisions at the LHC.

Formalism and Method

Results and Discussion

Summary and Conclusions