Diffractive photoproduction of heavy quarks in hadronic collisions

In this letter we study the diffractive photoproduction of heavy quarks in hadronic (pp/pA/AA) interactions for Tevatron and LHC energies. The integrated cross section and rapidity distribution for the process h_1 h_2 --> h_1 h_2 QQBAR (h_i = p,A and Q = c,b) are estimated using the Color Glass Condensate (CGC) formalism. Our results indicate that this production channel has larger cross sections than the competing reactions of double diffractive production and coherent AA reactions initiated by two-photon collisions.Comment: 4 pages, 2 figures, 1 table. Version to be published in Physical Review

Photoproduction of ρ0\rho^0 mesons in ultraperipheral heavy ion collisions at energies available at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC)

We investigate the photoproduction of $\rho$ mesons in ultraperipheral heavy ion collisions at RHIC and LHC energies in the dipole approach and within two phenomenological models based on the the Color Glass Condensate (CGC) formalism. We estimate the integrated cross section and rapidity distribution for meson production and compare our predictions with the data from the STAR collaboration. In particular, we demonstrate that the total cross section at RHIC is strongly dependent on the energy behavior of the dipole-target cross section at low energies, which is not well determined in the dipole approach. In contrast, the predictions at midrapidities at RHIC and in the full rapidity at LHC are under theoretical control and can be used to test the QCD dynamics at high energies.Comment: 6 pages, 5 figures, 1 table. Improved version to be published in Physical Review

The AGL Equation from the Dipole Picture

The AGL equation includes all multiple pomeron exchanges in the double logarithmic approximation (DLA) limit, leading to an unitarized gluon distribution in the small x regime. This equation was originally obtained using the Glauber-Mueller approach. We demonstrate in this paper that the AGL equation and, consequently, the GLR equation, can also be obtained from the dipole picture in the double logarithmic limit, using an evolution equation, recently proposed, which includes all multiple pomeron exchanges in the leading logarithmic approximation. Our conclusion is that the AGL equation is a good candidate for an unitarized evolution equation at small x in the DLA limit.Comment: 16 pages, 2 figures. Accepted for publication in Nuc. Phys.

Gluon saturation and the Froissart bound: a simple approach

At very high energies we expect that the hadronic cross sections satisfy the Froissart bound, which is a well-established property of the strong interactions. In this energy regime we also expect the formation of the Color Glass Condensate, characterized by gluon saturation and a typical momentum scale: the saturation scale $Q_s$. In this paper we show that if a saturation window exists between the nonperturbative and perturbative regimes of Quantum Chromodynamics (QCD), the total cross sections satisfy the Froissart bound. Furthermore, we show that our approach allows us to describe the high energy experimental data on $pp/p\bar{p}$ total cross sections.Comment: 6 pages, 5 figures. Includes additional figures, discussion and reference

Vector Meson Production in Coherent Hadronic Interactions: An update on predictions for RHIC and LHC

In this letter we update our predictions for the photoproduction of vector mesons in coherent $pp$ and $AA$ collisions at RHIC and LHC energies using the color dipole approach and the Color Glass Condensate (CGC) formalism. In particular, we present our predictions for the first run of the LHC at half energy and for the rapidity dependence of the ratio between the $J/\Psi$ and $\rho$ cross sections at RHIC energies.Comment: 4 pages, 3 figure

Gluon saturation and Feynman scaling in leading neutron production

In this paper we extend the color dipole formalism to the study of leading neutron production in $e + p \rightarrow e + n + X$ collisions at high energies and estimate the related observables, which were measured at HERA and may be analysed in future electron-proton ($ep$) colliders. In particular, we calculate the Feynman $x_F$ distribution of leading neutrons, which is expressed in terms of the pion flux and the photon-pion total cross section. In the color dipole formalism, the photon-pion cross section is described in terms of the dipole-pion scattering amplitude, which contains information about the QCD dynamics at high energies and gluon saturation effects. We consider different models for the scattering amplitude, which have been used to describe the inclusive and diffractive $ep$ HERA data. Moreover, the model dependence of our predictions with the description of the pion flux is analysed in detail. We show that the recently released H1 leading neutron spectra can be reproduced using the color dipole formalism and that these spectra could help us to observe more clearly gluon saturation effects in future $ep$ colliders.Comment: 10 pages, 5 figure