Chemical freeze-out parameters via a nonperturbative QCD approach

By analyzing the calculated baryon number susceptibility ratios chi(B)(1)/chi(B)(2) and chi(B)(3)/chi(B)(1) in a two-flavor system via the Dyson-Schwinger equation approach of QCD, we determine the chemical freeze-out temperature and baryon chemical potential in cases of both thermodynamic limit and finite size. We calculate the center-of-mass energy dependence of the chi(B)(4)/chi(B)(2)(kappa sigma(2)) at the freeze-out line and find an excellent agreement with experimental data when taking into account the finite size effect. Our calculations indicate that the kappa sigma(2) exhibits a nonmonotonic behavior in the lower collision energy region. We also predict that the collision energy dependence of chi(B)(6)/chi(B)(2) is nonmonotonic.