An introduction to leading and next-to-leading BFKL

TL;DR

BFKL theory seeks the high-energy behavior of perturbative QCD scattering by resumming terms of the form $(\\alpha_s \\ln s)^n$. The article discusses the historical LL prediction and the tension with experimental energy growth, then highlights the unexpectedly large and sometimes problematic next-to-leading corrections. It presents a framework that anchors BFKL insights within the DGLAP evolution and surveys resummation approaches to stabilize predictions at NLL and beyond. The work underscores the need for resummation to obtain reliable cross-section behavior and sets the stage for practical implementations in high-energy QCD phenomenology.

Abstract

Of late, the field of BFKL physics has been the subject of significant developments. The calculation of the NLL terms was recently completed, and they turned out to be very large. Techniques have been proposed to resum these corrections. These lectures provide an introduction to the BFKL equation and some of the recent developments, using DGLAP evolution as the starting point.