Ordering multiple soft gluon emissions using Glauber-SCET

TL;DR

This paper uses soft-collinear effective theory with Glauber operators to derive the coherence of multiple soft gluon emissions in QCD, emphasizing the role of the Lipatov vertex and paving the way for higher-loop analyses.

Contribution

It introduces a novel EFT-based derivation of soft gluon emission coherence, clarifying the underlying physics and extending the methodology to higher loop orders.

Findings

One-loop IR finiteness explained by transverse momentum.

Role of Lipatov vertex in coherence elucidated.

Framework established for higher-order calculations.

Abstract

In QCD, the amplitude for multiple soft gluon emissions has been shown to exhibit a form of coherence, wherein one-loop corrections are rendered IR finite by the transverse momentum of the real emissions. Using a sequence of soft-collinear effective theories (SCET) with Glauber operators, we present a compact and elegant derivation of this property. Our derivation highlights an important role played by the Lipatov vertex. The EFT approach provides increased physical intuition and, for the first time, a clear road map for how this result can be extended to higher loop orders.