Quark spin - thermal vorticity alignment and the Lambda, anti-Lambda polarization in heavy-ion collisions

TL;DR

This paper models the interaction between quark spin and thermal vorticity in heavy-ion collisions, calculating the relaxation time for polarization alignment considering finite quark mass and linking it to observed Lambda polarization.

Contribution

It provides a finite-temperature, finite-baryon chemical potential calculation of quark spin-vorticity relaxation time, incorporating quark mass effects and an effective interaction model.

Findings

Quark mass reduces the relaxation time for spin-vorticity alignment.

Intrinsic quark/antiquark polarization is linked to Lambda and anti-Lambda polarization.

Finite temperature and chemical potential influence the polarization dynamics.

Abstract

It has been proposed that the $\Lambda$ and $\overline{\Lambda}$ polarizations observed in heavy-ion collisions are due to the interaction between quark spin and thermal vorticity. In this work we report on a computation of the relaxation time required for this alignment to occur at finite temperature and baryon chemical potential, considering quarks with a finite mass. The calculation is performed after modelling the interaction by means of an effective vertex which couples the thermal gluons and quarks within the vortical medium. We show that the effect of the quark mass is to reduce the relaxation time as compared to the massless quark case. An intrinsic global polarization of quarks/antiquarks emerges which is shown to be linked with the $\Lambda$/$\bar{\Lambda}$ polarization.