Chemical freeze-out parameters via a functional renormalization group approach

We study the freeze -out parameters in a QCD-assisted effective theory that accurately captures the quantum and in -medium effects of QCD at low energies. The functional renormalization group approach is implemented in our work to incorporate the nonperturbative quantum, thermal, and density fluctuations. By analyzing the calculated baryon number susceptibility ratios chi 2B=chi 1B and chi 3B=chi 2B, we determine the chemical freeze -out temperatures and baryon chemical potentials in cases of hard thermal or dense loop improved mu-dependent gluon potential and mu-independent gluon potential. We calculate the chi 4B=chi 2Bo kappa sigma 2 thorn and chi 6B=chi 2B along the freeze -out line for both cases. It is found that kappa sigma 2 exhibits a nonmonotonic behavior in a low collision energy region and approaches one for lower collision energy. chi 6B=chi 2B shows a similar complicated behavior in our calculation.