Spin polarization and correlation of quarks from glasma

TL;DR

This paper explores how strong color fields in the glasma stage of high-energy nuclear collisions influence quark spins, revealing significant spin correlations that surpass vorticity effects but do not fully match experimental data.

Contribution

It provides a perturbative quantum kinetic theory framework for calculating quark spin polarization and correlations in a glasma background, highlighting mechanisms affecting spin alignment.

Findings

Quark-spin polarization vanishes for the Golec-Biernat Wüsthoff dipole distribution.

Nonzero out-of-plane spin correlation of quarks and antiquarks is found.

Estimated spin correlations exceed those caused by vorticity effects.

Abstract

We investigate the interaction of strong color fields in the glasma stage of high-energy nuclear collisions with the spins of quarks and antiquarks. We employ the perturbative solution of the quantum kinetic theory for the spin transport of (massive) quarks in a background color field governed by the linearized Yang-Mills equation and derive expressions for the quark-spin polarization and quark-antiquark spin correlation at small momentum in terms of field correlators. For the Golec-Biernat W\"usthoff dipole distribution the quark-spin polarization vanishes, but the out-of-plane spin correlation of quarks and antiquarks is nonzero. Our order-of-magnitude estimate of the correlation far exceeds that caused by vorticity effects, but does not fully explain the data for vector meson alignment. We identify possible mechanisms that could further increase the predicted spin correlation.