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

TL;DR

This paper investigates the polarization splitting between Lambda and anti-Lambda particles using the PICR hydrodynamic model, revealing unexpected effects related to baryon density gradients and collision centrality that align with experimental observations.

Contribution

It introduces a meson field mechanism within the PICR hydrodynamic model to explain polarization splitting and uncovers novel effects influencing the phenomenon.

Findings

Baryon density gradient negatively impacts polarization splitting.

Polarization splitting increases as collision centrality decreases at 7.7 GeV.

Model results align well with experimental data.

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.