We compute the distribution functions for gluons at very small $x$ and not too large values of transverse momenta. We extend the McLerran-Venugopalan model by using renormalization group methods to integrate out effects due to those gluons which generate an effective classical charge density for Weizsäcker-Williams fields. We argue that this model can be extended from the description of nuclei at small $x$ to the description of hadrons at yet smaller values of $x$. This generates a Lipatov-like enhancement for the intrinsic gluon distribution function and a nontrivial transverse momentum dependence as well. We estimate the transverse momentum dependence for the distribution functions, and show how the issue of unitarity is resolved in lepton-nucleus interactions.

• Received 6 August 1996

DOI:https://doi.org/10.1103/PhysRevD.55.5414