Investigating different $\Lambda$ and $\bar\Lambda$ polarizations in relativistic heavy-ion collisions

TL;DR

This study uses chiral kinetic equations within a partonic transport model to analyze how magnetic fields and quark interactions influence $ ext{Lambda}$ and $ar{ ext{Lambda}}$ polarization in relativistic heavy-ion collisions, revealing complex sensitivities.

Contribution

It demonstrates that $ ext{Lambda}$ and $ar{ ext{Lambda}}$ polarization differences are affected by quark interactions, challenging their use as direct magnetic field probes.

Findings

Magnetic fields increase spin polarization splitting compared to vacuum.

Quark-antiquark interactions significantly influence $ ext{Lambda}$ and $ar{ ext{Lambda}}$ polarization.

Large polarization splitting at 7.7 GeV cannot be explained by partonic dynamics.

Abstract

Based on the chiral kinetic equations of motion, spin polarizations of various quarks, due to the magnetic field induced by spectator protons as well as the quark-antiquark vector interaction, are studied within a partonic transport approach. Although the magnetic field in QGP enhances the splitting of the spin polarizations of partons compared to the results under the magnetic field in vacuum, the spin polarizations of $s$ and $\bar s$ quarks are also sensitive to the quark-antiquark vector interaction, challenging that the different $\Lambda$ and $\bar \Lambda$ spin polarization is a good measure of the magnetic field in relativistic heavy-ion collisions. It is also found that there is no way to obtain the large splitting of the spin polarization between $\Lambda$ and $\bar \Lambda$ at $\sqrt{s_{NN}}=7.7$ GeV with partonic dynamics.