Vorticity and $\Lambda$ polarization in the microscopic transport model PACIAE

TL;DR

This paper investigates the behavior of vorticities and $ ext{Lambda}$ polarization in non-central Au+Au collisions across a range of energies using the PACIAE microscopic transport model, revealing energy-dependent decay patterns and a non-monotonic initial vorticity dependence.

Contribution

It introduces a detailed analysis of four types of vorticities and their energy dependence, along with a method to reproduce global $ ext{Lambda}$ polarization using an energy density freeze-out criterion.

Findings

Vorticities decay faster at lower energies and smaller impact parameters.

Initial vorticities show a non-monotonic dependence on collision energy with a turning point at 10-15 GeV.

Global $ ext{Lambda}$ polarization is successfully reproduced across energies using the proposed criterion.

Abstract

We study the behavior of four types of vorticities in non-central Au+Au collisions at energies $\sqrt{S_{NN}}$ = 5--200 GeV using a microscopic transport model PACIAE. The results show that the vorticities decay faster at lower energy and smaller impact parameter. The non-monotonic dependence of the initial vorticities on the collision energies is reconfirmed and the turning point is 10-15 GeV for different vorticities. The global $\Lambda$ polarization at energies $\sqrt{S_{NN}}$ = 7.7--200 GeV is reproduced by introducing an energy density freeze-out criterion.