Photon polarisation in electron-seeded pair-creation cascades

TL;DR

This paper investigates the role of photon polarisation in electron-seeded pair-creation cascades within intense electromagnetic fields, deriving new rates and demonstrating how polarisation influences particle production rates.

Contribution

It derives rates for nonlinear Compton scattering and pair creation with arbitrary photon polarisation and includes these effects in numerical simulations, highlighting the impact of polarisation on cascade dynamics.

Findings

Unpolarised cross-sections approximate polarised ones within 5%.

Photon polarisation asymmetry can significantly enhance process rates.

Simulations support using unpolarised cross-sections for certain conditions.

Abstract

An electromagnetic pair-creation cascade seeded by an electron or a photon in an intense plane wave interacts in a complicated way with the external field. Many simulations neglect the vector nature of photons by including their interaction using unpolarised cross-sections. After deriving rates for the tree-level processes of nonlinear Compton scattering and pair creation with an arbitrary linearly-polarised photon in a constant-crossed field, we present results of numerical simulations that include the photon's vector nature. The simulations of seed electrons in a rotating electric field of optical frequency on the one hand support the approximation of using unpolarised cross-sections for tree-level processes, which predicts the same number of created particles when using polarised cross-section to within around 5 percent. On the other hand, these simulations show that when the polarisation of the photon can be influenced by its environment, the asymmetry in the polarisation distribution could be used to significantly increase the rates of each process.