Abstract
The particle yields and particle number ratios in Pb+Pb collisions at the LHC energy $\sqrt{s_{NN}}=2.76$ TeV are described within the integrated hydrokinetic model (iHKM) at the two different equations of state (EoS) for the quark-gluon matter and the two corresponding hadronization temperatures, $T=165$ MeV and $T=156$ MeV. The role of particle interactions at the final afterburner stage of the collision in the particle production is investigated by means of comparison of the results of full iHKM simulations with those where the annihilation and other inelastic processes (except for resonance decays) are switched off after hadronization/particlization, similarly as in the thermal models. An analysis supports the picture of continuous chemical freeze-out in the sense that the corrections to the sudden chemical freeze-out results, which arise because of the inelastic reactions at the subsequent evolution times, are noticeable and improve the description of particle and number ratios. An important observation is that although the particle number ratios with switched-off inelastic reactions are quite different at different particlization temperatures which are adopted for different equations of state to reproduce experimental data, the complete iHKM calculations bring very close results in both cases.
Highlights
The analysis of the particle number ratios is carried out successfully in thermal models for different energies of A + A collisions, from BNL Alternating Gradient Synchrotron (AGS) to CERN Large Hadron Collider (LHC) energies [1,2,3,4,5,6,7]
The ALICE Collaboration has already noted [8,9] that annihilation processes at the afterburner stage, which are taken into account in the hydrokinetic model (HKM) [10], noticeably improve agreement withproton spectra/yield at the LHC
In the current paper we present the results for different particle number ratios and spectra, calculated in integrated hydrokinetic model (iHKM) at two different particlization temperatures, Tp = 165 MeV and Tp = 156 MeV, with two corresponding equations of state (EoS) for quark-gluon matter: the Laine-Schröder EoS [20] and the HotQCD Collaboration (HotQCD) EoS [21]
Summary
The analysis of the particle number ratios is carried out successfully in thermal models for different energies of A + A collisions, from BNL Alternating Gradient Synchrotron (AGS) to CERN Large Hadron Collider (LHC) energies [1,2,3,4,5,6,7]. Sudden kinetic freeze-out means an instant change of hadron cross section from a very large one (typical for near perfect hydrodynamics) to zero cross section (free streaming particles). Such sudden transitions are not typical for realistic dynamical models.. We analyze the situation with different equations of state for quark-gluon and hadron matter and, correspondingly, at different temperatures of the so-called chemical freeze-out
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