Nonlinear lepton-photon interactions in external background fields

TL;DR

This paper investigates complex nonlinear lepton-photon interactions within general periodic background fields, extending existing models to high-energy regimes and deriving comprehensive probability formulas for phenomena like Compton scattering and pair production.

Contribution

It introduces a semi-classical approach using Volkov states to derive closed-form probabilities for nonlinear lepton-photon processes in arbitrary periodic backgrounds, including high-energy regimes.

Findings

Derived general formulas for nonlinear Compton scattering and pair production probabilities.

Identified additive contributions in the highly nonlinear regime.

Compared harmonic contributions for various field parameters.

Abstract

Nonlinear phenomena of lepton-photon interactions in external backgrounds with a generalised periodic plane-wave geometry are studied. We discuss nonlinear Compton scattering in head-on lepton-photon collisions extended properly to beyond the soft-photon regime. In addition, our results are applied to stimulated lepton-antilepton pair production in photon collisions with unrestricted energies. Derivations are considered semi-classically based on unperturbed fermionic Volkov representations encoding the full interaction with the background field. Closed expressions for total probabilities considering S-matrix elements have been derived. The general formula is applied to Compton scattering by an electron propagating in an external laser-like background. We obtain additive contributions in the extended unconstrained result which turns out to be stringently required in the highly nonlinear regime. A detailed comparison of contributing harmonics is discussed for various field parameters.