We study inclusive dijet azimuthal decorrelations in proton-proton collisions at the CERN LHC invoking the hypothesis of parton Reggeization in t−channel exchanges at high energies. In the parton Reggeization approach, the main contribution to the azimuthal angle difference between the two most energetic jets is due to the Reggeon-Reggeon-particle-particle scattering, when the fusion of two Reggeized gluons into a pair of Yang-Mills gluons dominates. Using a high-energy factorization scheme with the Kimber-Martin-Ryskin unintegrated parton distribution functions and the Fadin-Lipatov effective vertices we obtain good agreement of our calculations with recent measurements by the ATLAS and CMS Collaborations at the CERN LHC.

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According to extensive theoretical studies of the high energy limit of QCD, inelastic interactions are dominated by the multi-Regge final states. The appropriate gauge-invariant objects, which simultaneously incorporate the transverse momentum degrees of freedom, are Reggeized gluons, quarks and antiquarks. In the present communication we extend parton Reggeization approach to Drell-Yan production of massive lepton pairs. The basic ingredient is a process of Reggeized quark-antiquark annihilation, QQ → γ ⋆ → l + l − , which is described by the Reggeon-Reggeonphoton effective vertex Γ γ QQ . We calculate transverse-momentum and invariant-mass distributions of Drell-Yan lepton pairs measured at the CERN SPS, FNAL Tevatron and CERN LHC in the different ranges of energy and rapidity. We focus on angular distributions of Drell-Yan leptons in different kinematical ranges. The obtained results are compared with the existing data and a good agreement is found. The predictions for future experiments for Drell-Yan lepton pair production at the CERN LHC have been made.

The technique of one-loop calculations for the processes involving Reggeized quarks is described in the framework of gauge invariant effective field theory for the Multi-Regge limit of QCD, which has been introduced by Lipatov and Vyazovsky. The rapidity divergences, associated with the terms enhanced by $\log (s)$, appear in the loop corrections in this formalism. The covariant procedure of regularization of rapidity divergences, preserving the gauge invariance of effective action is described. As an example application, the one-loop correction to the propagator of Reggeized quark and $\gamma Q q$-scattering vertex are computed. Obtained results are used to construct the Regge limit of one-loop $\gamma\gamma\to q\bar q$ amplitude. The cancellation of rapidity divergences and consistency of the effective field theory prediction with the full QCD result is demonstrated. The rapidity renormalization group within the effective field theory is discussed.Comment: 11 pages, 2 figure

The hadroproduction of prompt isolated photon pairs at high energies is studied in the NLO framework of the Parton Reggeization Approach. The real part of the NLO corrections is computed, and the procedure for the subtraction of double counting between real parton emissions in the hardscattering matrix element and unintegrated PDF is constructed for the amplitudes with Reggeized quarks in the initial state. The matrix element of the important NNLO subprocess RR → γγ with full dependence on the transverse momenta of the initial-state Reggeized gluons is obtained. We compare obtained numerical results with diphoton spectra measured at Tevatron and the LHC, and find a good agreement of our predictions with experimental data at the high values of diphoton transverse momentum, p T , and especially at the p T larger than the diphoton invariant mass, M .In this multi-Regge kinematics region, the NLO correction is strongly suppressed, demonstrating the self consistency of the Parton Reggeization Approach.