Matching excluded-volume hadron-resonance gas models and perturbative QCD to lattice calculations

Abstract

We match three hadronic equations of state at low energy densities to a perturbatively computed equation of state of quarks and gluons at high energy densities. One of them includes all known hadrons treated as point particles, which approximates attractive interactions among hadrons. The other two include, in addition, repulsive interactions in the form of excluded volumes occupied by the hadrons. A switching function is employed to make the crossover transition from one phase to another without introducing a thermodynamic phase transition. A chi-square fit to accurate lattice calculations with temperature 100 < T < 1000 MeV determines the parameters. These parameters quantify the behavior of the QCD running gauge coupling and the hard core radius of protons and neutrons, which turns out to be 0.62 ± 0.04 fm. The most physically reasonable models include the excluded volume effect. Not only do they include the effects of attractive and repulsive interactions among hadrons, but they also achieve better agreement with lattice QCD calculations of the equation of state. The equations of state constructed in this paper do not result in a phase transition, at least not for the temperatures and baryon chemical potentials investigated. It remains to be seen how well these equations of state will represent experimental data on high energy heavy ion collisions when implemented in hydrodynamic simulations.

Thermalization in a small hadron gas system and high-multiplicity pp events

“…Recent LQCD simulations at finite temperature reveal existence of a de-confined partonic phase at high temperature and a confined hadronic phase at low temperature. The hadronic phase of the QCD medium is successfully addressed also by the Hadron Resonance Gas (HRG) Model [10][11][12], in statistical thermodynamic framework. An ideal HRG, formulated with discrete mass spectrum of * Electronic address: prem@vecc.gov.in identified hadrons and resonances, has been reinforced with the ab-initio confirmation [13][14][15][16] from the LQCD.…”

van der Waals hadron resonance gas and QCD phase diagram

“…Lattice simulations [8] of quantum chromodynamics (QCD) at vanishing baryon chemical potential (μ B ), corresponding to top-RHIC and LHC energies, provide reliable equation of state (EoS) for both the phases of strongly interacting matter, partonic and hadronic. The hadronic phase of the QCD matter [1,2] at zero μ B can be described successfully also by the hadron resonance gas (HRG) model [9][10][11]. The QCD matter at nonzero μ B , like the ones created [12] in heavy-ion collisions at comparatively lower center-of-mass energies ( √ s NN ) in the beam energy scan (BES) program at RHIC, however, is less understood.…”

Quasiparticle theory of transport coefficients for hadronic matter at finite temperature and baryon density

“…In previous papers, we investigated the equation of state at finite baryon chemical potential [10,11]. In this work, we derive new formulas to compute the shear and bulk viscosities and thermal conductivity of hot hadronic matter with µ B > 0.…”