Inclusive Gluon Production in DIS at High Parton Density

TL;DR

This work derives a single inclusive gluon production cross section for deep inelastic scattering at high parton density, incorporating nonlinear small-$x$ evolution and multiple rescatterings. The authors show that pre-emission evolution is linear while post-emission evolution is nonlinear, implementable via the adjoint-dipole amplitude $N_G$, and formulate a factorized, $k_T$-like expression in the large nucleus limit. They analyze the transverse momentum and rapidity dependence, revealing regions with perturbative ($1/k_ot^4$) behavior and saturation-dominated ($1/k_ot^2$) behavior, and propose an ansatz for gluon multiplicities in AA collisions including nonlinear evolution. The results provide a framework for predicting (mini)jet production in DIS and offer guidance for extending saturation-based descriptions to heavy-ion collisions, with potential relevance to RHIC phenomenology.

Abstract

We calculate the cross section of a single inclusive gluon production in deep inelastic scattering at very high energies in the saturation regime, where the parton densities inside hadrons and nuclei are large and the evolution of structure functions with energy is nonlinear. The expression we obtain for the inclusive gluon production cross section is generated by this nonlinear evolution. We analyze the rapidity distribution of the produced gluons as well as their transverse momentum spectrum given by the derived expression for the inclusive cross section. We propose an ansatz for the multiplicity distribution of gluons produced in nuclear collisions which includes the effects of nonlinear evolution in both colliding nuclei.

Figures (7)

• Figure 1: Gluon production in DIS in the quasi-classical approximation. The produced gluon may be emitted either off the quark or off the antiquark lines both in the amplitude and in the complex conjugate amplitude. Only one connection is shown.
• Figure 2: Emission of a harder gluon in the dipole evolution. Gluons are denoted by double lines in the large $N_c$ limit. The produced gluon is marked by a cross.
• Figure 3: One of the diagrams contributing to the class of graphs represented by Fig. \ref{['eem']}E.
• Figure 4: Another set of graphs contributing to emission of a harder gluon in the dipole evolution.
• Figure 5: Diagrams including one softer gluon produced after the emission of the measured gluon.