Different space-time freeze-out picture -- an explanation of different $\Lambda$ and $\bar{\Lambda}$ polarization?

Understand

Thermal vorticity in non-central Au+Au collisions at energies $7.7 \leq \sqrt{s} \leq 62.4$ GeV is calculated within the UrQMD transport model.

• Tracing the $\Lambda$ and $\bar{\Lambda}$ hyperons back to their last interaction point we were able to obtain the temperature and the chemical potentials at the time of emission by fitting the extracted bulk characteristics of hot and dense medium to statistical model of ideal hadron gas.
• Then the polarization of both hyperons was calculated.
• The polarization of $\Lambda$ and $\bar{\Lambda}$ increases with decreasing energy of nuclear collisions.