From dlogs to dilogs; the super Yang-Mills MHV amplitude revisited

TL;DR

This paper presents a new dlog-based method for computing planar 1-loop MHV amplitudes in N=4 super Yang-Mills theory, incorporating Feynman i epsilon prescription and extending to higher loops.

Contribution

It introduces a novel dlog integrand formulation for the planar 1-loop MHV amplitude, including regularization and potential for higher-loop calculations.

Findings

Kermit diagram is dual conformal invariant up to reference twistor.

New formulae relate nontrivially to previous literature.

Techniques extend to higher loops, demonstrated with a 2-loop example.

Abstract

Recently, loop integrands for certain Yang-Mills scattering amplitudes and correlation functions have been shown to be systematically expressible in dlog form, raising the possibility that these loop integrals can be performed directly without Feynman parameters. We do so here to give a new description of the planar 1-loop MHV amplitude in N = 4 super Yang-Mills theory. We explicitly incorporate the standard Feynman i epsilon prescription into the integrands. We find that the generic MHV diagram contributing to the 1-loop MHV amplitude, known as Kermit, is dual conformal invariant up to the choice of reference twistor explicit in our axial gauge (the generic MHV diagram was already known to be finite). The new formulae for the amplitude are nontrivially related to previous ones in the literature. The divergent diagrams are evaluated using mass regularization. Our techniques extend directly to higher loop diagrams, and we illustrate this by sketching the evaluation of a non-trivial 2-loop example. We expect this to lead to a simple and efficient method for computing amplitudes and correlation functions with less supersymmetry and without the assumption of planarity.