Narrow Results

In this paper, we review recent progress in the description of unpolarized transverse-momentum-dependent (TMD) gluon distributions at small $x$ in the color glass condensate (CGC) effective theory. We discuss the origin of the nonuniversality of TMD gluon distributions in the TMD factorization framework and in the CGC theory and the equivalence of the two approaches in their overlapping domain of validity. We show some applications of this equivalence, including recent results on the behavior of TMD gluon distributions at small $x$, and on the study of gluon saturation. We discuss recent advances in the unification of the TMD evolution and the nonlinear small-$x$ evolution of gluon distributions.

In this paper we discuss calculation of power corrections to the transverse momentum dependent (TMD) factorization which describes production of a particle with small transverse momentum in a hadron-hadron collision. As an example we consider power corrections to the TMD factorization formula for Z-boson production. We demonstrate that in the leading order in N_c power corrections can be expressed in terms of leading-twist TMDs which is a consequence of QCD equations of motion.