A new gauge-invariant double copy for heavy-mass effective theory

TL;DR

This paper introduces a gauge-invariant double-copy framework for heavy-mass effective theories, providing explicit BCJ numerators that are local, gauge-invariant, and satisfy key algebraic relations, applicable to tree amplitudes in Yang-Mills and gravity.

Contribution

It presents a novel gauge-invariant double-copy construction for heavy-mass effective theories with explicit BCJ numerators fixed by field strengths.

Findings

Explicit BCJ numerators constructed up to six particles.

Numerators are local, gauge-invariant, and satisfy Jacobi relations.

Connections established between heavy-mass BCJ numerators and pure Yang-Mills amplitudes.

Abstract

We propose a new form of the colour-kinematics/double-copy duality for heavy-mass effective field theories, which we apply to construct compact expressions for tree amplitudes with heavy matter particles in Yang-Mills and in gravity to leading order in the mass. In this set-up, the new BCJ numerators are fixed uniquely and directly written in terms of field strengths, making gauge invariance manifest. Furthermore, they are local and automatically satisfy the Jacobi relations and crossing symmetry. We construct these BCJ numerators explicitly up to six particles. We also discuss relations of the BCJ numerators in the heavy-mass effective theory with those in pure Yang-Mills amplitudes.