Universality of multi-particle production in QCD at high energies

TL;DR

This paper investigates multi-particle production in high-energy QCD collisions, revealing that complex multi-point functions are generally necessary but simplify to dipoles and quadrupoles in the large-N_c limit, demonstrating a form of universality.

Contribution

It proves that in the large-N_c limit, all multi-particle production processes can be described using only dipoles and quadrupoles within the Color Glass Condensate framework.

Findings

Higher-point functions like sextupoles and octupoles appear in cross sections.

In the large-N_c limit, multi-particle processes simplify to dipoles and quadrupoles.

Analytical sextupole form cannot generally be expressed as dipoles and quadrupoles.

Abstract

By studying the color structure of multi-particle production processes in p+A-type (dilute-dense) collisions, we find that higher-point functions beyond typical dipoles and quadrupoles, e.g., sextupoles, octupoles, etc., naturally appear in the cross sections, but are explicitly suppressed in the large-N_c limit. We evaluate the sextupole in the McLerran-Venugopalan model and find that, in general, its analytical form cannot be written as combination of dipoles and quadrupoles. Within the Color Glass Condensate framework, we present a proof that in the large-N_c limit, all multi-particle production processes in the collision of a dilute system off a dense can, up to all orders in \alpha_s, be described in terms of only dipoles and quadrupoles.