Unitarity corrections from the high energy QCD effective action

TL;DR

This paper derives reggeon transition vertices from Lipatov's high energy QCD effective action, focusing on the reduction to transverse form and verifying key vertices like BFKL and 2-to-3 transitions, with initial results on 2-to-4 transitions.

Contribution

It provides a detailed derivation of reggeon transition vertices from Lipatov's effective action, including the BFKL kernel and verification of the 2-to-3 vertex, with preliminary work on 2-to-4 vertices.

Findings

Derived the BFKL kernel from the effective action.

Verified the vanishing of the 2-to-3 reggeon transition vertex.

Discussed initial results on the 2-to-4 reggeon transition vertex.

Abstract

We investigate the derivation of reggeon transition vertices from Lipatov's gauge invariant effective action for high energy processes in QCD. In particular we address the question of longitudinal integrations in order to reduce the vertices into the required purely transverse form. We explicitly derive the BFKL-kernel and verify vanishing of the 2-to-3 reggeon transition vertex. First results on the derivation of the 2-to-4 reggeon transition vertex are discussed.