The NLO jet vertex for Mueller-Navelet and forward jets in the small-cone approximation

We calculate in the next-to-leading order the impact factor (vertex) for the production of a forward high-$p_T$ jet, in the approximation of small aperture of the jet cone in the pseudorapidity-azimuthal angle plane. The final expression for the vertex turns out to be simple and easy to implement in numerical calculations.Comment: 4 pages, 4 figures; presented at the XX International Workshop on Deep-Inelastic Scattering and Related Subjects, 26-30 March 2012, University of Bon

The γ∗γ∗\gamma^* \gamma^* total cross section in next-to-leading order BFKL and LEP2 data

We study the total cross section for the collision of two highly-virtual photons at large energies, taking into account the BFKL resummation of energy logarithms with full next-to-leading accuracy. A necessary ingredient of the calculation, the next-to-leading order impact factor for the photon to photon transition, has been calculated by Balitsky and Chirilli using an approach based on the operator expansion in Wilson lines. We extracted the result for the photon impact factor in the original BFKL calculation scheme comparing the expression for the photon-photon total cross section obtained in BFKL with the one recently derived by Chirilli and Kovchegov in the Wilson-line operator expansion scheme. We perform a detailed numerical analysis, combining different, but equivalent in next-to-leading accuracy, representations of the cross section with various optimization methods of the perturbative series. We compare our results with previous determinations in the literature and with the LEP2 experimental data. We find that the account of Balitsky and Chirilli expression for the photon impact factor reduces the BFKL contribution to the cross section to very small values, making it impossible to describe LEP2 data as the sum of BFKL and leading-order QED quark box contributions.Comment: 20 pages, 8 figures; two sentences and some references added, a few typos removed; version to be published on JHE

Semihard processes with BLM renormalization scale setting

We apply the BLM scale setting procedure directly to amplitudes (cross sections) of several semihard processes. It is shown that, due to the presence of $\beta_0$-terms in the NLA results for the impact factors, the obtained optimal renormalization scale is not universal, but depends both on the energy and on the process in question. We illustrate this general conclusion considering the following semihard processes: (i) inclusive production of two forward high-$p_T$ jets separated by large interval in rapidity (Mueller-Navelet jets); (ii) high-energy behavior of the total cross section for highly virtual photons; (iii) forward amplitude of the production of two light vector mesons in the collision of two virtual photons.Comment: 4 pages, one figure; presented by B. Murdaca at "Diffraction 2014", International Workshop on Diffraction in High-Energy Physics, Primosten (Croatia), Sept. 10-16, 2014; to be published in the conference proceedings by AI

Mueller-Navelet jets in next-to-leading order BFKL: theory versus experiment

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 center-of-mass energy of 7 TeV. The adopted jet vertices are calculated in the approximation of 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 thereafter our results with the experimental data from the CMS collaboration.Comment: 20 pages, 11 figures. Misprints removed in Tables 7 and 8 and in one place of the text; figures and conclusions unchanged; version which incorporates the Erratum accepted by Eur. Phys. J.