Two aspects of the Regge limit in QCD: Double Logs in Exclusive observables and Infrared Effects in Cross Sections

摘要

Two relevant points related to the application of the BFKL formalism tophenomenology are discussed. First, we have presented a set of observablescharacterizing multi-jet configurations event by event (average transversemomentum, average azimuthal angle, average ratio of jet rapidities) which canbe used to find distinct signals of BFKL dynamics at the LHC. A numericalanalysis has been shown using the Monte Carlo event generator BFKLex, modifiedto include higher-order collinear corrections in addition to thetransverse-momentum implementation of the NLO kernel. We require to have twotagged forward/backward jets in the final state. Second, the structure of theBFKL equation changes if infrared boundary conditions are imposed whenconsidering the running of the coupling. The cut in the complex angularmomentum plane becomes an infinite series of Regge poles. Integrating along acontour off the real axis we find a strong dependence of the intercepts andcollinear regions on the choice of the boundary conditions. The mean transversescales dominant in the gluon ladder increase. This could have interestingphenomenological consequences.