The (gamma^*-q\bar q)-Reggeon Vertex in Next-to-Leading Order QCD

TL;DR

This work computes the one-loop (NLO) corrections to the coupling of the reggeized gluon to the γ^* → qq̄ vertex, as a foundational step toward the NLO photon impact factor for γ^*γ^* scattering in the BFKL framework. By performing a high-energy analysis of γ^* q → q q̄ q, the authors derive explicit, diagram-by-diagram contributions, separating ultraviolet and infrared effects, and express results in a helicity basis with logarithmic and dilogarithmic functions. After renormalization in the MSbar scheme, UV poles cancel, leaving IR divergences to cancel only when all NLO pieces of the photon impact factor are combined in a future calculation. The study provides a detailed, albeit non-summed, set of results for the reggeon–photon vertex corrections, laying groundwork for a complete NLO treatment of γ^*γ^* scattering at high energy and offering important cross-checks and limit analyses for the BFKL program.

Abstract

As a first step towards the computation of the NLO corrections to the photon impact factor in the $γ^*γ^* \to γ^* γ^*$ scattering process, we calculate the one loop corrections to the coupling of the reggeized gluon to the $γ^*\to q\bar{q}$ vertex. We list the results for the Feynman diagrams which contribute: all loop integrations are carried out, and the results are presented in the helicity basis of photon, quark, and antiquark.

Figures (3)

• Figure 1: Contributions to the photon impact factor.
• Figure 2: Kinematics of the process $\gamma^* + q \to q\bar{q} + q$.
• Figure 3: Feynman diagrams for the process $\gamma^* + q \to q\bar{q} + q$.