Scattering of Gluons from the Color Glass Condensate

TL;DR

The paper analyzes gluon production in hadron collisions with dense targets using the Color Glass Condensate and classical Yang-Mills framework. It demonstrates a factorization of the inclusive gluon production cross section into the projectile gluon distribution and the target's classical-field scattering cross section, and derives the gluon-proton (nucleus) inelastic cross section at high energy. It contrasts perturbative and saturation regimes: perturbative cross sections scale as $1/p_T^4$ and grow with energy, while saturation yields an $O(1)$ cross section per unit area with logarithmic energy growth and introduces $A^{1/3}$ jet broadening. It also provides predictions for forward-region jet broadening and discusses model dependence of the saturation scale and area parameter.

Abstract

We prove that the inclusive single-gluon production cross section for a hadron colliding with a high-density target factorizes into the gluon distribution function of the projectile, defined as usual within the DGLAP collinear approximation, times the cross section for scattering of a single gluon on the strong classical color field of the target. We then derive the gluon-proton (nucleus) inelastic cross section and show that it is (up to logarithms) infrared safe and that it grows slowly with center of mass energy. Furthermore, we discuss jet transverse momentum broadening for the case of nuclear targets. We show that in the saturation regime, in contrast to the perturbative regime, the width of the transverse momentum distribution is infrared finite and grows rapidly with energy and rapidity. In both regimes, however, transverse momentum broadening exibits the same dependence on atomic number A.

Figures (1)

• Figure 1: Gluon production in inclusive $pp$ scattering at rapidity far from the target proton (i.e., the strong color field).