On the $k_{\perp }$ dependent gluon density in hadrons and the photon

The $k_{\perp }$ dependent gluon distribution for protons, pions,and photons is calculated accounting for the resummation of small~$x$ effects due to the Lipatov equation. It is represented by a convolution of a gluon density in the collinear limit and a universal function $\mathcal{G}(x,k^2,\mu )$ for which an analytic expression is derived.