Quantum kinetic theory for quantum chromodynamics

Abstract

We develop a quantum kinetic theory for QCD, which incorporates all leading order collision terms. The diagonal components of the Wigner functions for quarks and gluons satisfy a spin-averaged Boltzmann equation. The non-diagonal components of the Wigner functions give spin polarization of on-shell quarks and gluons in quark-gluon plasma induced by hydrodynamic gradients. A power counting in the coupling shows the spin polarization behaves differently in vortical and non-vortical gradients: the former is free of collisional contribution to leading order, while the latter contains a collisional contribution at parametrically the same order as the free theory counterpart. We also find the inelastic collision in a spin basis provides a possible mechanism for conversion between spin and orbital angular momentum.