$\Lambda/{\bar \Lambda}$ Polarization and Splitting Induced by Rotation and Magnetic Field

TL;DR

This paper investigates how rotation and magnetic fields induce polarization and splitting of $ar{ ext{Lambda}}$ and Lambda particles in a quark model, aligning well with experimental data.

Contribution

It introduces a dynamical quark model considering axial vector interactions and quark magnetic moments to explain polarization phenomena.

Findings

Rotation causes same-sign polarization of quarks and antiquarks.

Magnetic field causes opposite-sign polarization, leading to splitting.

The model's results agree with experimental measurements.

Abstract

The global polarization of $\Lambda/{\bar \Lambda}$ and the splitting of ${\bar \Lambda}-\Lambda$ polarization induced by rotation and magnetic field has been investigated in a dynamical quark model by taking into account the axial vector interaction and the anomalous magnetic moment of quarks. It is found that the rotation leads to the spin polarization of quarks and anti-quarks with the same sign, while the magnetic field to opposite sign, which corresponds to the ${\bar \Lambda}-\Lambda$ polarization splitting. The combination of the two effects leads to perfect agreement with experiment data. Quantitatively, the axial vector spin polarization contributes 30$\%$ of the global polarization and the anomalous magnetic moment of quarks contributes 40$\%$ to the splitting of ${\bar \Lambda}-\Lambda$ polarization. However, at $\sqrt{s_{NN}} \leq 7.7 \text{GeV}$, it still remains a challenge to reach enough magnitude of the magnetic field at freeze-out.