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We consider within QCD collinear factorization the process p + p → jet + jet + X, where two forward high-p T jets are produced with a large separation in rapidity ∆y (Mueller-Navelet jets). In this case the (calculable) hard part of the reaction receives large higher-order corrections ∼ α n s (∆y) n , which can be accounted for in the BFKL approach with next-to-leading logarithmic accuracy, including contributions ∼ α n s (∆y) n−1 . We calculate several observables related with this process, using the next-to-leading order jet vertices, recently calculated in the approximation of small aperture of the jet cone in the pseudorapidity-azimuthal angle plane. †

The Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach for the investigation of semihard processes is plagued by large next-to-leading corrections, both in the kernel of the universal BFKL Green's function and in the process-dependent impact factors, as well as by large uncertainties in the renormalization scale setting. All that calls for an optimization procedure of the perturbative series. In this respect, one of the most common methods is the Brodsky-Lepage-Mackenzie (BLM) one, which eliminates the renormalization scale ambiguity by absorbing the nonconformal β 0 terms into the running coupling. In this paper, we apply the BLM scale setting procedure directly to the amplitudes (cross sections) of several semihard processes. We show that, due to the presence of β 0 terms in the next-to-leading expressions for the impact factors, the optimal renormalization scale is not universal but depends both on the energy and on the type of process in question.

We investigate the stability under variation of the renormalization, factorization and energy scales entering the calculation of the cross section, at next-to-leading order in the BFKL formalism, for the production of Mueller-Navelet jets at the Large Hadron Collider, following the experimental cuts on the tagged jets. To find optimal values for the scales involved in this observable it is possible to look for regions of minimal sensitivity to their variation. We show that the scales found with this logic are more natural, in the sense of being more similar to the squared transverse momenta of the tagged jets, when the BFKL kernel is improved with a resummation of collinear contributions than when the treatment is at a purely next-to-leading order. We also discuss the good perturbative convergence of the ratios of azimuthal angle correlations, which are quite insensitive to collinear resummations and well described by the original BFKL framework.

We define new observables sensitive to Balitsky-Fadin-Kuraev-Lipatov (BFKL) dynamics in the context of multijet production at the Large Hadron Collider. We propose the study of the inclusive production of three jets well separated in rapidity from each other, with two of them being very forward. We show that the tagging of a third jet in the central region of rapidity allows for a very strong test of the BFKL formalism. In particular, we have studied two projections on azimuthal angles for the differential cross section which allow for the definition of many different observables whose behavior when varying the p t and rapidity of the central jet is a distinct signal of BFKL dynamics. In order to reduce the theoretical uncertainties and influence of higher order corrections, we propose the study of ratios of correlation functions of products of cosines of azimuthal angle differences among the tagged jets.

We study, within QCD collinear factorization and including BFKL resummation at the next-to-leading order, the production of Mueller-Navelet jets at LHC with centerof-mass energy of 7 TeV. The adopted jet vertices are calculated in the approximation of a small aperture of the jet cone in the pseudorapidity-azimuthal angle plane. We consider several representations of the dijet cross section, differing only beyond the next-to-leading order, to calculate a few observables related with this process. We use various methods of optimization to fix the energy scales entering the perturbative calculation and compare our results with the experimental data from the CMS collaboration.

No abstract

We calculate in the BFKL approach the jet vertex relevant for the production of Mueller-Navelet jets in proton-proton collisions. We consider both cases of incoming quark and gluon and show explicitly that all infrared divergences cancel when renormalized parton densities are considered. Finally we compare our expression for the vertex with a previous calculation [1].Comment: 4 pages, presented at the International Workshop 'Diffraction 2012', Puerto del Carmen (Spain), September 10-15, 201