BFKL predictions at small x from k_T and collinear factorization viewpoints

Abstract

Hard scattering processes involving hadrons at small $x$ are described by a $k_T$-factorization formula driven by a BFKL gluon. We explore the equivalence of this description to a collinear-factorization approach in which the anomalous dimensions $γ_{gg}$ and $γ_{qg}/α_S$ are expressed as power series in $α_S \log (1/x)$, or to be precise $α_S/ω$ where $ω$ is the moment index. In particular we confront the collinear-factorization expansion with that extracted from the BFKL approach with running coupling included.