2022 Impact factor 4.4
Particles and Fields

Eur. Phys. J. C 16, 337-347
DOI 10.1007/s100520000369

Structure function of the nucleus in the perturbative QCD
with $N_c\rightarrow\infty$(BFKL pomeron fan diagrams)

M. Braun

Department of High Energy Physics, University of St. Petersburg, 198904 St. Petersburg, Russia

Received: 26 January 2000 / Published online: 8 June 2000 - © Springer-Verlag 2000

The equation for the sum of BFKL pomeron fan diagrams is rederived by a direct summation and solved numerically for rapidities $y\leq 50$. At high rapidities, y>20, the resulting cross-sections for the scattering of a longitudinally polarized $q\bar q$ pair on the nucleus cease to depend on its transverse dimension and tend to a constant limit of 0.1768 RA2, 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 $Q^2\ln(1/x)$. 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.

Copyright Società Italiana di Fisica, Springer-Verlag 2000