Spin and polarisation dependent LCFA rates for nonlinear Compton and Breit-Wheeler processes

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In this paper we derive and discuss the completely spin- and photon-polarisation dependent probability rates for nonlinear Compton scattering and nonlinear Breit-Wheeler pair production.

• The locally constant field approximation, which is essential for applications in plasma-QED simulation codes, is rigorously derived from the strong-field QED matrix elements in the Furry picture for a general plane-wave background field.
• We discuss important polarisation correlation effects in the spectra of both processes.
• Asymptotic limits for both small and large values of $\chi$ are derived and their spin/polarisation dependence is discussed.