Excitation Function of Kinetic Freeze-Out Parameters at 6.3, 17.3, 31, 900 and 7000 GeV

Muhammad Waqas,Muhammad Ajaz,Atef Abdelkader,Abd Al Karim Haj Ismail

doi:10.3390/universe8020138

Abstract

The transverse momentum spectra of π+ (π−)(π++π−) at 6.3, 17.3, 31, 900 and 7000 GeV are analyzed by the blast-wave model with Tsallis statistics (TBW) in proton-proton collisions. We took the value of flow profile n0 = 1 and 2 in order to see the difference in the results of the extracted parameters in the two cases. Different rapidity slices at 31 GeV are also analyzed, and the values of the related parameters, such as kinetic freeze-out temperature, transverse flow velocity and kinetic freeze-out volume, are obtained. The above parameters rise with the increase of collision energy, while at 31 GeV, they decrease with increasing rapidity, except for the kinetic freeze-out volume, which increases. We also extracted the parameter q, which is an entropy-based parameter, and its rising trend is noticed with increasing collision energy, while at 31 GeV, no specific dependence of q is observed on rapidity. In addition, the multiplicity parameter N0 and mean transverse momentum are extracted, which increase with increasing collision energy and decrease with increasing rapidity. We notice that the kinetic freeze-out temperature and mean transverse momentum are slightly larger with n0 = 2, while the transverse flow velocity is larger in the case of n0 = 1, but the difference is very small and hence insignificant.

Highlights

In high-energy heavy-ion nucleus-nucleus collisions, an extremely hot and dense matter called the quark-gluon plasma (QGP) is formed
We reported that q slightly increased with energy, but did not have a specific trend with rapidity. q was comparatively lower at lower energies, which means that the system was closer to an equilibrium state due to the fact that the evolution process was slower at lower energies and the system took more time to reach the equilibrium state. q was observed to be slightly larger at n0 = 1
(2) We reported that T0 increases with the rise of collision energy due to the higher degree of excitation of the system at higher energies, and decreases with increasing the rapidity due to decreasing the transfer of energy towards forward rapidities

Summary

Introduction

In high-energy heavy-ion nucleus-nucleus collisions, an extremely hot and dense matter called the quark-gluon plasma (QGP) is formed. There are various kinds of temperatures, and they describe the excitation function of the interacting system at different evolution stages [1,2,3,4,5]. The mean transverse momentum (< pT >) spectra of the particles are used [6,7,8,9,10] for describing the excitation degree of the interacting system. The elastic interaction does not stop until the kinetic freeze-out stage is reached, where the transverse momentum (pT) spectra of the particles remain unchanged. The temperature at this stage is said to be the kinetic/thermal freeze-out temperature (T0). The effective temperature is a kind of temperature that includes the impact of flow effects

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Results

Conclusion