On the Coulomb corrections to the total cross section of the interaction of the π+π−\pi^+\pi^- atom with ordinary atoms at high energy

The size of $\pi^+\pi^-$ atom in the low lying states is considerably smaller than the radius of atomic screening. Due to that we can neglect this screening calculating the contribution of multi-photon exchanges. We obtain the analytic formula for Coulomb corrections which works with a very good accuracy for the ground state of $\pi^+\pi^-$ atom.Comment: 9 pages, LATEX with 1 Postscript figur

Hadron annihilation into two photons and backward dVCS in the scaling regime of QCD

We study the scaling regime of hadron-(anti)-hadron annihilation into a deeply virtual photon and a real photon, H anti-H -> gamma^* gamma, and deep backward virtual Compton scattering, gamma^* H -> H gamma. We advocate that there is a kinematical region where the scattering amplitude factorizes into a short-distance matrix element and a long-distance dominated object: a transition distribution amplitude which describes the hadron to photon transition.Comment: 4 pages, 1 .eps figure, to be published in Phys. Rev. D Rapid Com

A complete NLL BFKL calculation of Mueller Navelet jets at LHC

For the first time, a next-to-leading BFKL study of the cross section and azimuthal decorrellation of Mueller Navelet jets is performed, i.e. including next-to-leading corrections to the Green's function as well as next-to-leading corrections to the Mueller Navelet vertices. The obtained results for standard observables proposed for studies of Mueller Navelet jets show that both sources of corrections are of equal and big importance for final magnitude and final behavior of observables, in particular for the LHC kinematics investigated here in detail. The astonishing conclusion of our analysis is that the observables obtained within the complete next-lo-leading order BFKL framework of the present paper are quite similar to the same observables obtained within next-to-leading logarithm DGLAP type treatment. This fact sheds doubts on general belief that the studies of Mueller Navelet jets at the LHC will lead to clear discrimination between the BFKL and the DGLAP dynamics.Comment: 5 pages, 2 figures, to appear in the proceedings of 18th International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2010), Florence, Italy, 19-23 Apr 201

First complete NLL BFKL calculation of Mueller Navelet jets at LHC

For the first time, a next-to-leading BFKL study of the cross section and azimuthal decorrellation of Mueller Navelet jets is performed, i.e. including next-to-leading corrections to the Green's function as well as next-to-leading corrections to the Mueller Navelet vertices. The obtained results for standard observables proposed for studies of Mueller Navelet jets show that both sources of corrections are of equal and big importance for final magnitude and final behavior of observables, in particular for the LHC kinematics investigated here in detail. The astonishing conclusion of our analysis is that the observables obtained within the complete next-lo-leading order BFKL framework of the present paper are quite similar to the same observables obtained within next-to-leading logarithm DGLAP type treatment. The only noticeable difference is the ratio the azimuthal angular moments / which still differs in both treatments.Comment: 5 pages, 1 figure, to appear in the proceedings of 35th International Conference on High Energy Physics, (ICHEP 2010), Paris, France, July 22-28, 201

On timelike and spacelike hard exclusive reactions

We show to next-to-leading order accuracy in the strong coupling alpha_s how the collinear factorization properties of QCD in the generalized Bjorken regime relate exclusive amplitudes for spacelike and timelike hadronic processes. This yields simple space--to--timelike relations linking the amplitudes for electroproduction of a photon or meson to those for photo- or meso-production of a lepton pair. These relations constitute a new test of the relevance of leading twist analyzes of experimental data.Comment: v2: major text revision; results, references, and author added; v3: matches the published version Phys. Rev. D86, rapid communication

Diffractive meson production from virtual photons with odd charge-parity exchange

We calculate the cross section of diffractive charge-parity C=+1 neutral meson production in virtual photon proton collision at high energies. Due to the opposite C-parities of photon and meson M (M = eta_C, pi^0, a_2) this process probes the t-channel C=-1 odderon exchange which is described here as noninteracting three-gluon exchange. Estimates for the cross section of the inelastic diffractive process gamma^* p -> eta_C X_p are presented. The total cross section of diffractive \eta_C meson photoproduction is found to be 47 pb. The cross sections for the diffractive production of light mesons (pi^0, a_2) in \gamma^* p collisions are of the same order if the photon virtuality Q^2 is m^2_C.Comment: LaTeX, 19 pages, 8 ps-figs, epsfi

Probing GPDs in Ultraperipheral Collisions

Ultraperipheral collisions in hadron colliders give new opportunites to investigate the hadron stucture through exclusive photoproduction processes. We describe the possibility of measuring the Generalized Parton Distributions in the Timelike Compton Scattering process and in the production of heavy vector meson.Comment: to appear in Proceedings Diffraction 2014, Primosten, Croatia, sept 10-16, 201

Probing GPDs in photoproduction processes at hadron colliders

Generalized parton distributions (GPDs) enter QCD factorization theorems for hard exclusive reactions. They encode rich information about hadron partonic structure. We explore a possibility to constrain GPDs in experiments at LHC considering two different exclusive processes: the timelike Compton scattering and the photoproduction of heavy vector mesons.Comment: 6 pages, 2 figures; presented at PHOTON 2015: International Conference on the Structure and the Interactions of the Photon, Novosibirsk, Russia, 15 - 19 June, 2015. arXiv admin note: text overlap with arXiv:1411.375