Progress on the soft anomalous dimension in QCD

TL;DR

This paper reviews IR singularities in multileg QCD amplitudes, introduces a new method using lightcone expansion of Wilson line correlators, and reports the three-loop soft anomalous dimension for single massive particles.

Contribution

It presents a novel strategy to compute the soft anomalous dimension using lightcone expansion and Method of Regions, enabling higher-loop calculations.

Findings

Determined the three-loop soft anomalous dimension for single massive particles with any number of massless ones.

The strategy facilitates future calculations involving two heavy particles at three loops.

The approach simplifies understanding of IR singularities in multileg QCD amplitudes.

Abstract

We review the state-of-the-art knowledge of IR singularities in multileg QCD amplitudes, identifying the key reasons for the remarkable simplicity of the soft anomalous dimension. We then present a novel strategy to compute this quantity using a lightcone expansion of correlators of semi-infinite Wilson lines by the Method of Regions. Recently, this strategy allowed us to determine the three-loop soft anomalous dimension for amplitudes consisting of a single massive coloured particle with any number of massless ones. It opens the way to computing this quantity for amplitudes involving two heavy particles at three loops and potentially going to higher loop orders.