Reggeon cuts in QCD amplitudes with negative signature

TL;DR

The paper addresses the breakdown of the pole Regge form in QCD amplitudes with negative signature at NNLLA due to Reggeon cuts, focusing on the three-gluon exchange contributions that generate a three-Reggeon cut. It analyzes lowest-order two-loop diagrams and radiative corrections to separate pole and cut effects, introducing coefficients such as $C_R$, $C_3$ and $C^C_{ij}$, $C^R_{ij}$ that must satisfy infrared factorization constraints. By matching non-factorizing three-loop remnants with Regge-cut contributions, the authors argue that the NNLLA BFKL framework must include Regge cuts in addition to Regge poles, with the total high-energy behavior encoded in a generalized kernel. This work clarifies the role of Regge cuts in the adjoint color channel, informing the derivation and consistency of the NNLLA BFKL equation and impacting the understanding of high-energy QCD phenomenology.

Abstract

Reggeon cuts in QCD amplitudes with negative signature are discussed. These cuts appear in the next-to-next-to-leading logarithmic approximation (NNLLA) and greatly complicate the derivation of the BFKL equation. Feynman diagrams responsible for appearance of these cuts are indicated and the cut contributions are calculated in the two- and three-loop approximation.

Figures (4)

• Figure 1: Three-gluon exchange diagrams
• Figure 2: Diagrammatic representation of $A^{(3)}_\perp$ in the transverse momentum space
• Figure 3: Diagrammatic representation of $A^{(3)}_\perp C_R$
• Figure 4: Diagrammatic representation of $A^{(3)}_\perp C_R$