Chemical freeze-out parameters via functional renormalization group approach

Abstract

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. Functional renormalization group approach is implemented in our work to incorporate the non-perturbative quantum, thermal and density fluctuations. By analyzing the calculated baryon number susceptibility ratios ${\chi }_2^B/{\chi }_1^B$ and ${\chi }_3^B/{\chi }_2^B$, we determine the chemical freeze-out temperatures and baryon chemical potentials in cases of hard thermal or dense loop improved $\mu$-dependent glue potential and $\mu$-independent glue potential. We calculate the ${\chi }_4^B/{\chi }_2^B(\kappa {\sigma }^2)$ and ${\chi }_6^B/{\chi }_2^B$ along the freeze-out line for both cases. It's found that $\kappa {\sigma }^2$ exhibits a nonmonotonic behavior in low collision energy region and approach to one for lower collision energy. ${\chi }_6^B/{\chi }_2^B$ shows a similar complicated behavior in our calculation.

Comments: 14 pages, 11 figures, 7 tables