Centrality dependence of kinetic freeze-out temperature and transverse flow velocity in high energy nuclear collisions

TL;DR

This study analyzes how the kinetic freeze-out temperature and transverse flow velocity depend on collision centrality and energy in high-energy nuclear collisions using the blast-wave model, revealing slight increases with centrality and energy and a dependence on particle mass.

Contribution

It applies the blast-wave model with Boltzmann-Gibbs statistics to a wide range of collision systems and energies, highlighting the size-dependent effects on freeze-out parameters.

Findings

Kinetic freeze-out temperature slightly increases with centrality and energy.

Transverse flow velocity shows a slight increase with centrality and energy.

Main parameters are mainly determined by the heaviest nucleus involved.

Abstract

Centrality-dependent double-differential transverse momentum spectra of charged pions, kaons, and (anti)protons produced in mid-pseudorapidity interval in $\sqrt{s_{NN}}=200$ GeV gold-gold and deuteron-gold collisions with different centralities are analyzed by the blast-wave model with Boltzmann-Gibbs statistics. Meanwhile, the mentioned spectra in mid-rapidity interval in $\sqrt{s_{NN}}=2.76$ TeV lead-lead and $\sqrt{s_{NN}}=5.02$ TeV proton-lead collisions with different centralities are analyzed by the same model. The model results are approximately in agreement with the experimental data in special transverse momentum ranges. It is shown that with the increase of event centrality and energy, the kinetic freeze-out temperature of the emission source and the transverse flow velocity of the produced particles slightly increase in some cases but they do not give an obvious change in other cases. Meanwhile, the kinetic freeze-out temperature (transverse flow velocity) increases (decreases) with the increase of particle mass. The average transverse momentum and initial temperature increase with the increase of event centrality, collision energy, and particle mass. This work also confirms the maximum size dependent effect, which states that the main parameters such as the kinetic freeze-out temperature and transverse flow velocity are mainly determined by the heaviest nucleus from proton-nucleus to nucleus-nucleus collisions.