Non-Perturbative High-Energy QCD

TL;DR

This paper reviews the non-perturbative aspects of high-energy QCD, emphasizing recent theoretical insights into the challenges of understanding scattering processes and the role of experimental data from HERA in advancing the field.

Contribution

It highlights the non-perturbative nature of high-energy QCD and discusses recent theoretical developments influenced by experimental results, especially in small-x deep inelastic scattering.

Findings

High-energy QCD scattering is fundamentally non-perturbative.

Lattice methods are ineffective for this regime.

HERA experiments have significantly impacted theoretical understanding.

Abstract

It is the aim of this talk to review our understanding of the high-energy limit of QCD, focussing, in particular, on recent theoretical developments. After a brief introduction, I will recall why the true high-energy limit of QCD scattering processes is genuinly non-perturbative and why it has so far not been possible to apply lattice methods to this type of physics. Given the experimental fact of slowly rising hadronic cross sections, we are thus faced with a fundamental problem comparable to that of confinement but without the promise of the lattice. During the last years, the experimental side of this field has largely been driven by the HERA accelerator, which has, naturally, also influenced recent theoretical work in high-energy QCD. I will therefore devote the second part of the talk to small-x deep inelastic scattering, in particular the physics of diffraction, and attempt to describe its impact on the wider field of non-perturbative high-energy QCD.