Thermodynamics of strongly interacting matter in a hybrid model

The equation of state and fluctuations of conserved charges in astrongly interacting medium under equilibrium conditions form thebaseline upon which are built various possible scenarios in relativisticheavy-ion collision experiments. Many of these quantities have beenobtained in the lattice QCD framework with reliable continuumextrapolations. Recently the Polyakov-Nambu-Jona-Lasinio model has beenreparametrized to some extent to reproduce quantitatively the latticeQCD equation of state at vanishing chemical potentials. The agreementwas precise except at low temperatures, possibly due to inadequaterepresentation of the hadronic degrees of freedom in the model. Thisdisagreement was also observed for some of the fluctuations andcorrelations considered. Here we address this issue by introducing theeffects of hadrons through the hadron resonance gas model. The totalthermodynamic potential is now a weighted sum of the thermodynamicpotential of the Polyakov-Nambu-Jona-Lasinio model and that of thehadron resonance gas model. We find that the equation of state and thefluctuations and correlations obtained in this hybrid model agreesatisfactorily with the lattice QCD data in the low temperature regime.