Holographic equation of state matched with hadron gas equation as a tool for the study of the quark-gluon plasma evolution

Abstract

In this paper, we discuss the matching of the holographic equation of state with the equation of Hadron Resonance Gas for studying the nuclear matter properties within the framework of relativistic heavy-ion collisions. Machine learning methods are applied to the calibration of model's free parameters using the lattice QCD results for the physical values of quark masses. One of the most advanced procedures for matching is used with the function that approximate behavior of both models on particular limit adopted from NEOS equation. Final hadronic spectra are obtained within multi-staged numerical approach of the iEBE-MUSIC and SMASH-vHLLE packages. The code of relativistic hydrodynamics is modified by implementing a tabulated holographic equation of state, enabling simulations of quark-gluon plasma evolution with dynamically generated initial conditions via the 3D Monte Carlo Glauber Model and SMASH. Hybrid iSS+UrQMD and Hadron Sampler+SMASH approaches are utilized at the freeze-out stage.

Figures (3)

• Figure 1: The result of fitting the ratio $\frac{s}{T^3}$ for isotropic (line in the picture on the left) and anisotropic (line in the picture on the right) models. The points for $T>0.18$ GeV are lattice results for the physical masses of quarks 2007jq. In the region of $T<0.18$GeV, we use as the points the results of the hadron gas equation obtained in the Thermal-FIST 2019pjl package
• Figure 2: The results of matching the holographic equation with the hadron gas equation for the isotropic (left) and anisotropic (right) cases. The empty and shaded circles indicate the predictions of holography and hadron gas, respectively, and the black grid corresponds to the result with matching.
• Figure 3: The results of the $m_T$ spectra calculations for $K^{+}$ in the MUSIC-UrQMD (left) and SMASH-vHLLE (right) approaches using the equation of state with matching. The solid line corresponds to the isotropic equation of state, when the dotted line is the anisotropic equation. The dot-and-dash line corresponds to the reference equation (NEOS 2019MSS in the case of iEBE-MUSIC, AZ Hydro 2012HFR for SMASH-vHLLE). The points were taken for experimental data NA49 2002pzu