A study of $\Lambda$ and $\bar{\Lambda}$ polarization splitting by meson field in PICR hydrodynamic model

Abstract

With the PICR hydrodynamic model, we study the polarization splitting between $\Lambda$ and $\bar{\Lambda}$ at RHIC BES energy range, based on the meson field mechanism. Our results fit to the experimental data fairly well. Besides, two unexpected effect emerges: (1) the baryon density gradient has non-trivial and negative contribution to the polarization splitting; (2) for 7.7 GeV Au+Au collisions within the centrality range of 20\%-50\%, the polarization splitting surprisingly increases with the centrality decreases. The second effect might help to explain the significant signal of polarization splitting measured in STAR's Au+Au 7.7 Gev collisions.