QCD Reggeon Field Theory for every day: Pomeron loops included

TL;DR

High-energy hadronic scattering in QCD faces unitarity challenges due to Pomeron loops. This work derives a Reggeon Field Theory Hamiltonian $H_{RFT}$, valid for arbitrary color densities, that resums Pomeron loop effects within the high-energy evolution. Building on the foam framework, it expresses the evolution in terms of Wilson lines and a Bogoliubov-coherent structure, yielding a kernel that unifies projectile-target dynamics. The resulting framework reproduces the known JIMWLK and KLWMIJ limits, bridges dense-dense and dense-dilute regimes, and enables numerical studies of Pomeron-loop dynamics in nucleus-nucleus collisions.

Abstract

We derive the evolution equation for hadronic scattering amplitude at high energy. Our derivation includes the nonlinear effects of finite partonic density in the hadronic wave function as well as the effect of multiple scatterings for scattering on dense hadronic target. It thus includes Pomeron loops. It is based on the evolution of the hadronic wave function derived in \cite{foam}. The kernel of the evolution equation defines the second quantized Hamiltonian of the QCD Reggeon Field Theory, $H_{RFT}$ beyond the limits considered so far. The two previously known limits of the evolution: dilute target (JIMWLK limit) and dilute projectile (KLWMIJ limit) are recovered directly from our final result. The Hamiltonian $H_{RFT}$ is applicable for the evolution of scattering amplitude for arbitrarily dense hadronic projectiles/targets - from "dipole-dipole" to "nucleus-nucleus" scattering processes.