We derive a quantum kinetic theory for QED based on Kadanoff-Baym equations for Wigner functions. By assuming parity invariance and considering a complete set of self-energy diagrams, we find that the resulting kinetic theory expanded to lowest order in $\hslash$ generalizes the well-known classical kinetic theory to the massive case. It contains elastic and inelastic collision terms and integrates a screening effect naturally. For a given solution to the classical kinetic theory, we find at next order in $\hslash$ a nondynamical quantum correction to Wigner functions for both fermions and photons, which gives rise to spin polarization for fermions and photons, respectively. The approach allows us to study the nondynamical part of the collisional effect on the spin polarization phenomenon.

• Received 10 January 2022
• Accepted 22 March 2022

DOI:https://doi.org/10.1103/PhysRevD.105.076017

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Published by the American Physical Society