Unintegrated parton distributions and correlation functions

We discuss the limitations of the standard collinear approach. The kinematical approximations necessary to derive the collinear factorization are insufficient for the description of the exclusive final states. We argue that for a proper treatment of the final states one needs to use fully unintegrated parton correlation functions. We introduce the gauge invariant definitions of these objects and the factorization theorem for one jet production in deep inelastic scattering.Comment: 6 pages, 3 figures, pdflatex. Talk presented at 12th International Conference on Elastic and Diffractive Scattering, Hamburg, DES

RHIC physics: short overview

This talk gives a very short overview of some of the important physical phenomena observed at the Relativistic Heavy Ion Collider (RHIC). The emphasis is put on the multiplicities, hard probes and the properties of the initial state.Comment: 8 pages, 5 figures, pdflatex. Talk presented at 12th International Conference on Elastic and Diffractive Scattering, in Hamburg, DES

Unintegrated Double Parton Distributions - a Summary

We present main elements of the construction of unintegrated double parton distribution functions which depend on transverse momenta of partons. We follow the method proposed by Kimber, Martin and Ryskin for a construction of unintegrated single parton distributions from the standard parton distribution functions.Comment: presented at "Diffraction 2016", International Workshop on Diffraction in High Energy Physics, Acireale (Catania, Sicily), Sept 2-8 2016, to be published in the conference proceedings by AI

Drell-Yan process at forward rapidity at the LHC

We analyze the Drell-Yan lepton pair production at forward rapidity at the Large Hadron Collider. Using the dipole framework for the computation of the cross section we find a significant suppression in comparison to the collinear factorization formula due to saturation effects in the dipole cross section. We develop a twist expansion in powers of Q_s^2/M^2 where Q_s is the saturation scale and M the invariant mass of the produced lepton pair. For the nominal LHC energy the leading twist description is sufficient down to masses of 6 GeV. Below that value the higher twist terms give a significant contribution.Comment: 13 pages, 7 figure

Small x resummation and the Odderon

We present a general argument which suggests that the Bartels-Lipatov-Vacca Odderon intercept should be equal to one to all orders in the perturbation theory. The argument is based on the validity of the so called omega-expansion in the high energy limit. It can be further supported by the analogous pattern observed in the case of the anomalous dimensions which is a consequence of the momentum sum rule. In addition, we conjecture that the BFKL kernel should satisfy the transverse momentum sum rule. Finally, it is shown that the higher order kinematical effects do not change the BLV Odderon intercept.Comment: 13 pages, 4 figure

BFKL Pomeron loop contribution in diffractive photoproduction and inclusive hadroproduction of J/ψJ/\psi and Υ\Upsilon

We analyze contributions to the heavy vector meson production with large transverse momentum in proton--proton and diffractive photon--proton scattering driven by an exchange of two Balitsky--Fadin--Kuraev--Lipatov Pomerons in the squared amplitudes. The Pomerons couple to a single parton and form a Pomeron loop closed by the vector meson impact factors. For the photon--proton case the diffractive cut of the Pomeron loop contributes, and for the inclusive hadroproduction one finds the loop with two cut Pomerons. We compute both of these Pomeron loop contributions and study in detail their properties. The results are then used to calculate the cross sections for diffractive $J/\psi$ photoproduction with large transverse momentum at HERA and the correlated two Pomeron contribution for inclusive $J/\psi$ and $\Upsilon$ production cross sections at the LHC. Within a unified approach a good description of the photoproduction data is found, but correlated two Pomeron mechanism gives only a small contribution to hadroproduction of the vector mesons at the LHC.Comment: 34 pages, 16 figure

Universality of multi-particle production in QCD at high energies

By studying the color structure of multi-particle production processes in p+A-type (dilute-dense) collisions, we find that higher-point functions beyond typical dipoles and quadrupoles, e.g., sextupoles, octupoles, etc., naturally appear in the cross sections, but are explicitly suppressed in the large-N_c limit. We evaluate the sextupole in the McLerran-Venugopalan model and find that, in general, its analytical form cannot be written as combination of dipoles and quadrupoles. Within the Color Glass Condensate framework, we present a proof that in the large-N_c limit, all multi-particle production processes in the collision of a dilute system off a dense can, up to all orders in \alpha_s, be described in terms of only dipoles and quadrupoles.Comment: 24 pages, 16 figures, Published in Phys.Rev.