One-loop central-emission vertex for two gluons in $\mathcal{N}=4$ super Yang-Mills theory

TL;DR

This paper computes the one-loop two-gluon central emission vertex in $ ext{N}=4$ super Yang-Mills theory, a key component for advancing high-energy QCD calculations to higher precision, by analyzing six-gluon amplitudes in a specific kinematic limit.

Contribution

It provides the first explicit calculation of the one-loop two-gluon CEV in $ ext{N}=4$ SYM, capturing complex amplitude structures and facilitating future QCD and BFKL equation developments.

Findings

Factorization of the dispersive part of six-gluon amplitude in terms of the two-gluon CEV.

Explicit expression for the one-loop two-gluon CEV for any helicity configuration.

The CEV's structure reflects the complexity of six-gluon amplitudes and simplifies in the MRK limit.

Abstract

A necessary ingredient for extending the BFKL equation to next-to-next-to-leading logarithmic (NNLL) accuracy is the one-loop central emission vertex (CEV) for two gluons which are not strongly ordered in rapidity. Here we consider the one-loop six-gluon amplitude in $\mathcal{N}=4$ super Yang-Mills (SYM) theory in a central next-to-multi-Regge kinematic (NMRK) limit, we show that its dispersive part factorises in terms of the two-gluon CEV, and we use it to extract the one-loop two-gluon CEV for any helicity configuration within this theory. This is a component of the two-gluon CEV in QCD. Although computed in the NMRK limit, both the colour structure and the kinematic dependence of the two-gluon CEV capture much of the complexity of the six-gluon amplitudes in general kinematics. In fact, the transcendental functions of the latter can be conveniently written in terms of impact factors, trajectories, single-emission CEVs and a remainder, which is a function of the conformally invariant cross ratios which characterise the six-gluon amplitudes in planar $\mathcal{N}=4$ SYM. Finally, as expected, in the MRK limit the two-gluon CEV neatly factorises in terms of two single-emission CEVs.