Speaker
Description
$\Lambda$ and $\bar{\Lambda}$ polarization in heavy-ion collisions at BES RHIC energies is studied within the microscopic transport model UrQMD. Two approaches, (1) thermal and (2) axial anomaly approach, are considered. We trace the formation and space-time evolution of vorticiity 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 antilambda 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.
