Chiral condensate and the Equation Of State at non-zero baryon density from hadron resonance gas model with repulsive mean-field

We study the QCD equation of state and the chiral condensate using the hadron resonance gas with repulsive mean-field interactions. We find that the repulsive interactions improve the agreement with the lattice results on the derivatives of the pressure with respect to the baryon chemical potential up to eighth order. From the temperature dependence of the chiral condensate we estimate the crossover temperature as a function of baryon chemical potential, T_c(μ_B). We find that the chiral crossover line starts to deviate significantly from the chemical freeze-out line already for μ_B>400 MeV. Furthermore, we find that the chiral pseudo-critical line can be parameterized as T_c(μ_B)/T_c(0)=1-κ_2 (μ_B/T_c (0))^2-κ_4 (μ_B/T_c (0))^4 with κ_2=0.0150(2) and κ_4=3.1(6) · 10^-5 which are in agreement with lattice QCD results for small values of μ_B. For the first time we find a tiny but non-zero value of κ_4 in our study.