Gluon Shadowing in DIS off Nuclei

TL;DR

This paper presents a detailed quantum-chromodynamics model for nuclear shadowing in deep-inelastic scattering at small Bjorken x, incorporating color transparency, coherence effects, and gluon suppression, with numerical solutions validated against experimental data.

Contribution

It introduces an exact numerical solution for the Green function evolution in a dipole formalism, improving accuracy over eikonal approximations at moderate xB values.

Findings

Gluon suppression significantly contributes to nuclear shadowing at xB < 0.01.

The model aligns well with E665 and NMC experimental data.

Predictions extend to very small xB relevant for LHC experiments.

Abstract

Within a light-cone quantum-chromodynamics dipole formalism based on the Green function technique, we study nuclear shadowing in deep-inelastic scattering at small Bjorken xB < 0.01. Such a formalism incorporates naturally color transparency and coherence length effects. Calculations of the nuclear shadowing for the \bar{q}q Fock component of the photon are based on an exact numerical solution of the evolution equation for the Green function, using a realistic form of the dipole cross section and nuclear density function. Such an exact numerical solution is unavoidable for xB > 0.0001, when a variation of the transverse size of the \bar{q}q Fock component must be taken into account. The eikonal approximation, used so far in most other models, can be applied only at high energies, when xB < 0.0001 and the transverse size of the \bar{q}q Fock component is "frozen" during propagation through the nuclear matter. At xB < 0.01 we find quite a large contribution of gluon suppression to nuclear shadowing, as a shadowing correction for the higher Fock states containing gluons. Numerical results for nuclear shadowing are compared with the available data from the E665 and NMC collaborations. Nuclear shadowing is also predicted at very small xB corresponding to LHC kinematical range. Finally the model predictions are compared and discussed with the results obtained from other models.