Helicity amplitudes in massless QED to higher orders in the dimensional regulator

TL;DR

This paper analytically computes one- and two-loop helicity amplitudes in massless QED for four-fermion and Compton scattering, employing a four-dimensional tensor decomposition to facilitate higher-order theoretical predictions.

Contribution

It introduces an efficient integrand-level algorithm for organizing loop amplitudes into integral families and explores the singular structure and QED-QCD correspondence.

Findings

Amplitudes expressed with generalized polylogarithms up to weight six.

Provides a systematic approach for higher-order QED calculations.

Analyzes the singularity structure and process correspondence.

Abstract

We analytically calculate one- and two-loop helicity amplitudes in massless QED, by adopting a four-dimensional tensor decomposition. We draw our attention to four-fermion and Compton scattering processes to higher orders in the dimensional regulator, as required for theoretical predictions at N$^3$LO. We organise loop amplitudes by proposing an efficient algorithm at integrand level to group Feynman graphs into integral families. We study the singular structure of these amplitudes and discuss the correspondence between QED and QCD processes. We present our results in terms of generalised polylogarithms up to transcendental weight six.