Speaker
Description
$\Lambda$ and $\bar{\Lambda}$ polarization in heavy-ion collisions at BES RHIC energies is studied within the microscopic transport model UrQMD. We trace the formation and space-time evolution of vorticity and helicity patterns in details. This study demands a complex analysis of the fireball conditions including time slices, extraction of temperature and baryo- and strangeness chemical potentials, as well as freeze-out conditions of both hyperons. Rapidity and transverse momentum dependence of the polarization are obtained. We show that difference in global polarization of $\Lambda$ and $\bar{\Lambda}$ at c.m. energies below 10 GeV can be explained by different space-time freeze-out conditions of two hyperons. Comparison with the STAR results shows a fair agreement between the model and the data.
