Small-x evolution with Q dependence and unitarity

Abstract

We propose a modified Balitsky-Fadin-Kuraev-Lipatov equation from the viewpoint of the resummation technique, which contains an intrinsic dependence on momentum transfer Q, and satisfies the unitarity bound. The idea is to relax the strong rapidity ordering and to restrict phase space for real gluon emissions in the evaluation of the BFKL kernel. It is shown that the power-law rise of the gluon distribution function with the small Bjorken variable x turns into a logarithmic rise, and that the predictions for the proton structure function $F_2(x,Q^2)$ are consistent with the HERA data.