AbstractWe introduce a novel approach based on elastic and inelastic scattering rates to extract the hyper-surface of the chemical freeze-out from a hadronic transport model in the energy range from E$$_\mathrm {lab}=1.23$$
lab
=
1.23
AGeV to $$\sqrt{s_\mathrm {NN}}=62.4$$
s
NN
=
62.4
GeV. For this study, the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model combined with a coarse-graining method is employed. The chemical freeze-out distribution is reconstructed from the pions through several decay and re-formation chains involving resonances and taking into account inelastic, pseudo-elastic and string excitation reactions. The extracted average temperature and baryon chemical potential are then compared to statistical model analysis. Finally we investigate various freeze-out criteria suggested in the literature. We confirm within this microscopic dynamical simulation, that the chemical freeze-out at all energies coincides with $$\langle E\rangle /\langle N\rangle \approx 1$$
⟨
E
⟩
/
⟨
N
⟩
≈
1
GeV, while other criteria, like $$s/T^3=7$$
s
/
T
3
=
7
and $$n_\mathrm {B}+n_{\bar{\mathrm {B}}}\approx 0.12$$
n
B
+
n
B
¯
≈
0.12
fm$$^{-3}$$
-
3
are limited to higher collision energies.
Fluctuations of conserved charges within a Hadron Resonance Gas approach: chemical freeze-out conditions from net-charge and net-proton fluctuations