Vorticity and Particle Polarization in Relativistic Heavy-Ion Collisions

TL;DR

This paper reviews the study of vortical motion and hyperon polarization in relativistic heavy-ion collisions, highlighting model predictions and the energy-dependent behavior of vorticity and vortex structures.

Contribution

It introduces 3FD model predictions for hyperon polarization and describes the energy-dependent evolution of vorticity and vortex structures in collisions.

Findings

Vorticity decreases with increasing collision energy in the central region.

At high energies, vorticity shifts to fragmentation regions forming vortex rings.

Hyperon polarization is linked to the vorticity distribution in the collision.

Abstract

We review studies of vortical motion and the resulting global polarization of $\Lambda$ and $\bar{\Lambda}$ hyperons in heavy-ion collisions, in particular, within 3FD model. 3FD predictions for the global midrapidity polarization in the FAIR-NICA energy range are presented. The 3FD simulations indicate that energy dependence of the observed global polarization of hyperons in the midrapidity region is a consequence of the decrease of the vorticity in the central region with the collision energy rise because of pushing out the vorticity field into the fragmentation regions. At high collision energies this pushing-out results in a peculiar vortical structure consisting of two vortex rings: one ring in the target fragmentation region and another one in the projectile fragmentation region with matter rotation being opposite in these two rings.