Obtaining fully polarised amplitudes in gauge invariant form

Abstract

We describe progress applying the \textit{Worldline Formalism} of quantum field theory to the fermion propagator dressed by $N$-photons to study multi-linear Compton scattering processes, explaining how this approach -- whose calculational advantages are well-known at multi-loop order -- yields compact and manifestly gauge invariant scattering amplitudes.

3 pages, 1 figure. Prepared for the Proceedings of the 20th Lomonosov Conference on Elementary Particle Physics, held in August 2021, based on a talk given by James P. Edwards on the results of [arXiv:2004.01391 [hep-th]] and [arXiv:2107.00199 [hep-th]