# Quantum Kinetic Theory of Spin Polarization of Massive Quarks in Perturbative QCD: Leading Log

## TL;DR

This paper derives a quantum kinetic equation describing the spin polarization evolution of massive quarks in a QCD plasma, valid for arbitrary quark masses much larger than the Debye mass, at leading logarithmic order in perturbative QCD.

## Contribution

It introduces a universal quantum kinetic equation for massive quark spin dynamics in perturbative QCD at leading log order, applicable for arbitrary large quark masses.

## Key findings

- Collision terms are of order α_s^2 log(1/α_s).
- Equation valid for quark masses much larger than the Debye mass.
- Provides a framework for studying spin relaxation in QCD plasma.

## Abstract

We present the quantum kinetic equation for spin polarization of massive quarks in leading log order of perturbative QCD, which describes time evolution of the spin density matrix in momentum space of a massive quark interacting with a background QCD plasma. We find that the time evolution operator of the spin density matrix, or the quantum kinetic collision terms, are universally of order $\alpha_s^2\log(1/\alpha_s)$ in terms of the QCD coupling constant $\alpha_s=g^2/(4\pi)$. Our quantum kinetic equation is valid for an arbitrary quark mass $m\gg m_D\sim gT$, where $m_D$ is the Debye mass, and can be used to study relaxation dynamics of spin polarization of massive quarks in perturbative QCD regime.