Abstract
The thermodynamic properties of matter created in high-energy heavy-ion collisions have been studied in the framework of the non-extensive Tsallis statistics. The transverse momentum (p_mathrm{T}) spectra of identified charged particles (pions, kaons, protons) and all charged particles from the available experimental data of Au-Au collisions at the Relativistic Heavy Ion Collider (RHIC) energies and Pb-Pb collisions at the Large Hadron Collider (LHC) energies are fitted by the Tsallis distribution. The fit parameters, q and T, measure the degree of deviation from an equilibrium state and the effective temperature of the thermalized system, respectively. The p_mathrm{T} spectra are well described by the Tsallis distribution function from peripheral to central collisions for the wide range of collision energies, from sqrt{s_mathrm{NN}} = 7.7 GeV to 5.02 TeV. The extracted Tsallis parameters are found to be dependent on the particle species, collision energy, centrality, and fitting ranges in p_mathrm{T}. For central collisions, both q and T depend strongly on the fit ranges in p_mathrm{T}. For most of the collision energies, q remains almost constant as a function of centrality, whereas T increases from peripheral to central collisions. For a given centrality, q systematically increases as a function of collision energy, whereas T has a decreasing trend. A profile plot of q and T with respect to collision energy and centrality shows an anti-correlation between the two parameters.
Highlights
IntroductionIn case of heavy-ion collisions, the transverse momentum spectra have traditionally been fitted by blast-wave model [16] [1,2,17–19]
Our study shows that the Tsallis parameters obtained by fitting the pT distributions vary with respect to the fitting range in pT, centrality of the collision and collision energy
We have analyzed the pT spectra of identified and all charged particles produced in Au–Au collisions at eight energies at Relativistic Heavy Ion Collider (RHIC) and Pb–Pb collisions at two energies at Large Hadron Collider (LHC) using a the non-extensive Tsallis statistics
Summary
In case of heavy-ion collisions, the transverse momentum spectra have traditionally been fitted by blast-wave model [16] [1,2,17–19] This model has a simple assumption that there is a kinetic freeze-out of the colliding medium at temperature Tkin and particles are moving with a common collective radial flow velocity (β). Recent studies [7] have found that the Tsallis statistics works in heavy-ion collisions providing good fitting of the pT spectra of all charged particles Since these fits do not account for the radial flow, the temperatures obtained from the Tsallis fits are the effective temperatures, different from the kinetic freezeout temperatures. We use the thermodynamically consistent form of the Tsallis distribution [8] to fit the transverse momentum ( pT) spectra of the identified charged particles with a focus on pions as well as all charged particles in heavy-ion collision systems corresponding to eight different collision energies at RHIC and two collision energies at the LHC. The dependencies of the fitting parameters on collision centrality, collision energy and fitting ranges in pT are
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