Constraining the chemical freeze-out with coarse-grained transport

Abstract

We use the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model to extract the microscopic chemical freeze-out hyper-surface from a dynamical hadronic transport simulation. By coarse-graining the output, the distribution of the temperature and the baryo-chemical potential can be extracted on this hyper-surface. The energy dependence of the average chemical freeze-out temperature and the average baryo-chemical potential follows the trend seen in the statistical model and also captures the data points of the chemical freeze-out curve very well. We finally check the established chemical freeze-out criteria with our method and indeed we can confirm the constant energy per particle criterion at all investigated energies, while the entropy density criterion and the baryon density criterion are fulfilled at larger collision energies.