Gluon shadowing in DIS off nuclei

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 xBj ≲ 0.01. Such a formalism incorporates naturally color transparency and coherence length effects. Calculations of the nuclear shadowing for the 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 xBj ≳ 10−4, when a variation of the transverse size of the 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 xBj ≲ 10−4 and the transverse size of the Fock component is ‘frozen’ during propagation through the nuclear matter. At xBj ⩽ 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 xBj corresponding to LHC kinematical range. Finally, the model predictions are compared and discussed with the results obtained from other models.