Numerical tools for the theoretical study of QCD at small x

In this contribution we present the status of two numerical tools designed to study the small x limit of QCD. The first one is a Monte Carlo simulation of the BFKL evolution equation. In design of this approach emphasis has been placed on exploiting the linear behaviour that many variants of the BFKL evolution possess. This allows us to design a procedure which can be used to study theoretical and phenomenological aspects of different kernels. The second one is a semi-analytic approach to study Lipatov's effective action which describes Reggeon interactions. The study of the properties of this action is very complicated and we propose using a computational tool to handle the large amount of non--local vertices and the derivation of higher order corrections.Comment: 7 pages, 3 figures. International Workshop on Diffraction in High-Energy Physics -DIFFRACTION 2006 - September 5-10 2006 Adamantas, Milos island, Greec

The High Energy Radiation Pattern from BFKLex

We discuss a recent study on high-energy jet production in the multi-Regge limit done with the use of the Monte Carlo event generator BFKLex which includes collinear improvements in the form of double-log contributions. We will show results for the average transverse momentum and azimuthal angle of the final state jets when at least one of them is very forward in rapidity and another one is very backward. We also discuss the introduction of a new observable which accounts for the average rapidity ratio among subsequent emissions.Comment: 6 pages, presented by G. Chachamis at the XXIV International Workshop on Deep-Inelastic Scattering and Related Subjects, 11-15 April 2016, DESY Hamburg, German

Order-by-order Analytic Solution to the BFKL Equation

We propose a regularization of the BFKL equation which allows for its solution in each order of perturbation theory by means of a sum over multiple poles. This sum can be presented in a rather simple formula for the Fourier transform in the azimuthal angle of the gluon Green function. In order to test our method, we have compared a few orders in the expansion to previous results by Del Duca, Dixon, Duhr and Pennington, finding agreement. Our formalism is general and can be applied to other, more complicated, kernels.Comment: 23 pages, 1 figur

The Effect of a Rapidity Gap Veto on the Discrete BFKL Pomeron

We investigate the sensitivity of the discrete BFKL spectrum, which appears in the gluon Green function when the running coupling is considered, to a lower cut-off in the relative rapidities of the emitted particles. We find that the eigenvalues associated to each of the discrete eigenfunctions decrease with the size of the rapidity veto. The effect is stronger on the lowest eigenfunctions. The net result is a reduction of the growth with energy for the Green function together with a suppression in the regions with small transverse momentum.Comment: 10 pages, 3 figure

Applications of Lipatov's high energy effective action to NLO BFKL jet phenomenology

We report on recent progress in the evaluation of next-to-leading order (NLO) observables using Lipatov's QCD high energy effective action. We calculate both real and virtual corrections to the quark induced forward jet vertex at NLO, making use of a new regularization method and a subtraction mechanism. As a new result we determine the real part of the NLO Mueller-Tang impact factor which is the only missing element for a complete NLO BFKL description of dijet events with a rapidity gap.Comment: 4 pages, 29 figures, proceedings of the XX Workshop on Deep-Inelastic Scattering and Related Subjects, 26-30 March, University of Bonn (2012

Using the BFKL resummation to fit DIS data: collinear and running coupling effects

The proton structure function F2 is studied in the low x regime using BFKL evolution. The next to leading logarithmic (NLL) analysis requires the inclusion of running coupling effects which lead to off-diagonal terms in the evolution kernel. An all-orders resummation is used to improve the collinear behavior of the NLL BFKL result. We emphasize the theoretical uncertainties that appear throughout the analysis and give a comparison to the combined HERA data.Comment: 4 pages, 5 figures, proceedings of the XX Workshop on Deep-Inelastic Scattering and Related Subjects, 26-30 March, University of Bonn (2012