Reduced cross-section in Electron-Ion Colliders at small x

The nuclear reduced cross section σAᵣ, in the kinematic range of the electron-Ion collider with center-of-mass energy √s=140~GeV and y≤1, is discussed. The importance of the nuclear longitudinal structure function FAL and its behavior owing to the impact parameter for the heavy and light nucleus of Pb-208 and C-12 at Q²=5 and 10~GeV² is considered. The dependence of the ratios RA_FL and RAσ on the impact parameter and the expanding point of the gluon density at small x are investigated. The factorized form of parton distributions in nuclei is used in HIJING2.0 model.