Chemical freeze-out parameters via a nonperturbative QCD approach

By analyzing the calculated baryon number susceptibility ratios χ1B/χ2B and χ3B/χ1B 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 χ4B/χ2B(κσ2) 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 κσ2 exhibits a nonmonotonic behavior in the lower collision energy region. We also predict that the collision energy dependence of χ6B/χ2B is nonmonotonic.