Spin Polarizations in a Covariant Angular-Momentum-Conserved Chiral Transport Model

TL;DR

This paper develops a covariant chiral transport model that conserves angular momentum and incorporates spin-orbit interactions, demonstrating how quark spin polarization arises dynamically in rotating quark matter and matches experimental observations.

Contribution

It introduces a novel covariant model with angular momentum conservation that accounts for spin polarization via side jumps in chiral fermion scatterings.

Findings

Side jumps can dynamically polarize quark spins in rotating quark matter.

The model's predictions align with experimental Lambda hyperon polarization data.

Local quark spin polarizations exhibit azimuthal angle dependence consistent with observations.

Abstract

Using a covariant and angular-momentum-conserved chiral transport model, which takes into account the spin-orbit interactions of chiral fermions in their scatterings via the side jumps, we study the quark spin polarization in quark matter. For a system of rotating and unpolarized massless quarks in an expanding box, we find that side jumps can dynamically polarize the quark spin and result in a final quark spin polarization consistent with that of thermally equilibrated massless quarks in a self-consistent vorticity field. For the quark matter produced in noncentral relativistic heavy ion collisions, we find that in the medium rest frame both the quark local spin polarizations in the direction perpendicular to the reaction plane and along the longitudinal beam direction show an azimuthal angle dependence in the transverse plane similar to those observed in experiments for the Lambda hyperon.