Structure function of the nucleus in the perturbative QCD with Nc → ∞ (BFKL pomeron fan diagrams)

The equation for the sum of BFKL pomeron fan diagrams is rederived by a direct summation and solved numerically for rapidities y less than or equal to 50. At high rapidities, y > 20, the resulting cross-sections for the scattering of a longitudinally polarized q (q) over bar pair on the nucleus cease to depend on its transverse dimension and tend to a constant limit of 0.1768R(A)(2), which corresponds to scattering of a color dipole on a black disk. Thus the unitarity is restored and the singularity in the j plane is reduced to a simple pole at j = 1. The nuclear structure function at small x behaves as Q(2)1n(1/x). The gluon density found has a soliton-like form in the log k space: its form is close to Gaussian, independent of rapidity, the center moving towards higher log k with a nearly constant velocity as the rapidity, increases.