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In this work the double vector meson production in two-photon interactions at high energies is investigated considering saturation physics. We extend the color dipole picture for this process and study the energy and virtuality dependence of the forward differential cross section. Comparison with previous results is presented and the contribution of the different photon polarizations is estimated., Comment: 20 pages, 8 figures, 1 table. Version to be published in European Physical Jornal C

We report on our recent investigations in photonuclear production of heavy quarks and vector meson in ultraperipheral heavy ion collisions. In particular, our theoretical predictions are compared with the recent experimental measurements on coherent rho (STAR) and J/Psi (PHENIX) photoproduction at RHIC and estimates for LHC are given., Comment: 6 pages, 1 figure. To appear in the proceedings of International Workshop on Astronomy and Relativistic Astrophysics (IWARA2005), 2-5 Oct. 2005, Natal, Brazil

At small-x, the structure function F_L(x,Q2) is driven by the gluon content of the nucleon target and consequently it can unravel the underlying QCD dynamics in that region. In this work, one studies its behavior on photon virtuality Q2 at fixed energy within the color dipole formalism for models considering parton saturation effects. The reason is that they resum a wide class of higher-twist contributions, which have important influence in F_L description towards low Q2. It is shown that the geometric scaling property holds for the longitudinal cross section. Moreover, the effective anomalous dimension in scaling dipole cross sections can be investigated by studing both the turn over and the large Q2 regions of the recent experimental measurements., Comment: 13 pages, 5 figures. Includes new analyzes as a comparison with NLO and NNLO QCD calculations. Some model predictions have been revised and title has a shorter version. Extended version to be published in European Physical Journal C

In this letter we study the photoproduction of heavy quarks and vector mesons in the coherent proton-nucleus (pA) interactions for RHIC and LHC energies and analyze if these processes can be used to determine the QCD dynamics at high energies. The integrated cross section and rapidity distribution are estimated using the Color Glass Condensate (CGC) formalism. A comparison with the linear dynamics predictions is also presented. Our results indicate that the nonlinear dynamics can be proven in those reactions, which are well suited for studing saturation effects., Comment: 5 pages, 3 figures. Version to be published in Physical Review C

The skewing factor, defined as the ratio of the imaginary parts of the amplitudes $Im A(\gamma^* p \to \gamma^* p)/Im A(\gamma^* p \to \gamma p)$ is extracted for the first time from the data using recent Deeply Virtual Compton Scattering (DVCS) and the inclusive inelastic cross section measurements at DESY-HERA. The results values are compared to theoretical predictions for NLO QCD and the colour dipole approach., Comment: 15 pages, 5 figures

In this work the double vector meson production in ultraperipheral heavy ion collisions is investigated within the BFKL approach. The integrated cross sections and event rates for the processes AA --> V1 V2 AA (V_i = rho, omega, phi, J/Psi, Upsilon) are computed and theoretical estimates for scattering on both light and heavy nuclei are given for energies of RHIC and LHC., Comment: 10 pages, 1 figure. Version to be published in the European Physical Journal C

The ultraperipheral heavy ion collisions (UPC's) are an important alternative to study the QCD dynamics until the next generation of $e^+e^-/ ep / eA $ colliders become reality. Due to the coherent action of all the protons in the nucleus, the electromagnetic field is very strong and the resulting flux of equivalent photons is large, which allows to study two-photon as well as photonuclear interactions at high energies. In this paper we present a brief review of the vector meson production in UPC's at high energies using the QCD color dipole approach to describe their photonuclear production and the perturbative QCD Pomeron (BFKL dynamics) to describe the double meson production in photon-photon process. Predictions for rates and integrated cross sections are presented for energies of RHIC and LHC., Comment: 16 pages, 1 figure. Version to be published in Journal of Physics G: Nuclear and Particle Physics

Based on the QCD dipole picture of the BFKL Pomeron, we investigate the role played by the saturation scale, Q_{sat}, in obtaining physical values for the affective strong coupling in phenomenological fits to small-x HERA data. The dependence on this scale appears since the collection of color dipoles characterizing the proton target have average size 1/Q_{sat}, which is energy dependent. Physically, this means most of the color dipoles are above but sufficiently close to the border between a saturated and the dilute system. The analysis is first performed in the leading-logs BFKL approach in the saddle-point approximation and it could shed light in further investigations using resummed NLO BFKL kernels

It is shown that in ultrahigh energy inelastic neutrino-nucleon(nucleus) scattering the cross sections for the boson-hadron(nucleus) reactions should exhibit geometric scaling on the single variable tau_A =Q2/Q2_{sat,A}. The dependence on energy and atomic number of the charged/neutral current cross sections are encoded in the saturation momentum Q_{sat,A}. This fact allows an analytical computation of the neutrino scattering on nucleon/nucleus at high energies, providing a theoretical parameterization based on the scaling property., Comment: 5 pages, 4 figures

The photonuclear production of vector mesons in ultraperipheral heavy ion collisions is investigated within the QCD color dipole picture, with particular emphasis on the saturation model. The integrated cross section and the rapidity distribution for the A + A --> V + A + A (V = rho, omega, phi, J/Psi) process are computed and theoretical estimates for scattering on both light and heavy nuclei are given for energies of RHIC and LHC. A comparison with the recent STAR data on coherent production of rho mesons is also presented. Furthermore, we calculate the photoproduction of vector mesons in proton-proton collisions at RHIC, Tevatron and LHC energies., Comment: 19 pages, 6 figures and 2 tables. Version to be published in Eur. Phys. J. C

Using the QCD dipole picture of the hard BFKL Pomeron, we perform a 3 parameter fit analysis of the recent inclusive structure function experimental measurements at small-$x$ and intermediate $Q^2$. As a byproduct, the longitudinal structure function and the gluon distribution are predicted without further adjustments. The data description is quite reasonable, being timely a further study using resummed NLO BFKL kernels along the lines of recent theoretical developments., Comment: Contribution to the ``International Workshop on Diffraction in High-Energy Physics'' (DIFFRACTION 2004), Cala Gonone (Sardinia, Italy), 18-23 September 2004; 3 pages, LaTeX file

We calculate the photoproduction of heavy quarks in proton-proton collisions at RHIC, Tevatron and LHC energies. The integrated cross section and the rapidity distributions for open charm and bottom production are computed employing sound high energy QCD formalisms. For the linear pQCD approaches we consider both the usual collinear factorization and the k_T-factorization formalisms, whereas for the nonlinear QCD (saturation) calculations one considers the Golec-Biernat-Wuesthoff and the Iancu-Itakura-Munier parameterizations for the dipole cross section within the color dipole picture., Comment: 15 pages, 5 figures. Version to be published in Physical Review D

The high parton density regime of the Quantum Chromodynamics (QCD), where the physics of parton saturation is expected to be dominant, is briefly discussed. Some phenomenological aspects of saturation are described, mainly focusing on possible signatures of the non-linear QCD dynamics in the heavy quark production in electron-proton/nucleus collisions. Implications of these effects in the heavy quark production in ultraperipheral heavy-ion collisions are also presented., Comment: Invited brief review for Mod. Phys. Lett. A, 15 pages, 3 figures; Refs added

We summarize here our investigations on the deeply virtual Compton scattering (DVCS) in the color dipole approach, implementing the dipole cross section through the saturation model. The role played by its QCD evolution and the skewedness effects in the DVCS cross section are discussed. The phenomenological results are compared to the recent H1 and ZEUS experimental data., Comment: 4 pages, 3 figures, Proceedings of the XIIth International Workshop on Deep Inelastic Scattering (DIS04), Strbske Pleso, Slovakia, April 14-18 2004

The longitudinal structure function in deep inelastic scattering is one of the observables from which the gluon distribution can be unfolded. Consequently, this observable can be used to constrain the QCD dynamics at small $x$. In this work we compare the predictions of distinct QCD models with the recent experimental results for $F_L(x,Q^2)$ at small $x$ and low $Q^2$ obtained by the H1 collaboration. We focus mainly on the color dipole approach, selecting those models which include saturation effects. Such models are suitable at this kinematical region and also resum a wide class of higher twist contributions to the observables. Therefore, we investigate the influence of these corrections to $F_L$ in the present region of interest., Comment: 13 pages, 3 figures. Version to be published in Eur. Phys. J. C

We calculate the nuclear cross section for vector meson exclusive photoproduction within the QCD color dipole picture and in the Regge approach. For the former approach, we have considered the phenomenological saturation model, whereas for the latter we use a model based on the dipole Pomeron framework. Theoretical estimates for scattering on both light and heavy nuclei are given for a large range on energy., Comment: 18 pages, 3 figures. Includes additional discussions, references and a comparison with the GLLMN model. Extended version to be published in Eur. Phys. J. C

We show the role played by QCD evolution and skewedness effects in the DVCS cross section at large $Q^2$ within the color dipole description of the process at photon level. The dipole cross section is given by the saturation model, which can be improved by DGLAP evolution at high photon virtualities. We investigate both possibilities as well as the off-forward effect through a simple phenomenological parametrisation. The results are compared to the recent ZEUS DVCS data., Comment: LaTeX, 6 pages, 5 Figs. Vers 2: Minor modifications. Accepted by EPJC

The diffractive open charm production is computed in perturbative QCD formalism and in the Regge approach. The results are compared with recent data on charm diffractive structure function measured at DESY-HERA. Our results demonstrate that this observable can be useful to discriminate the QCD dynamics., Comment: LaTeX, 13 pages, 2 figures. Version to be published in Phys. Lett. B

The ultrahigh energy neutrino-nucleon cross sections are computed taking into account different phenomenological implementations of the non-linear QCD dynamic s. Based on the color dipole framework, the results for the saturation model supplemented by DGLAP evolution as well as for the BFKL formalism in the geometric scaling regime are presented. They are contrasted with recent calculations using NLO DGLAP and unified BFKL-DGLAP formalisms., Comment: 5 pages, 2 figures. Version to be published in Physical Review D

We investigate the Drell-Yan transverse momentum distribution in the framework of the color dipole approach. Special attention is paid to parton saturation effects at high energies. Predictions at LHC energies ($\sqrt{s}=14$ TeV) are given and extrapolated down to ISR energies ($\sqrt{s}=62$ GeV). Unitarity corrections are implemented through the multiple scattering Glauber-Mueller approach and are compared with predictions of the BGBK saturation model., Comment: 6 pages, 2 figures. Contribution to 11th International Workshop on Deep-Inelastic Scattering (DIS03), St. Petersburg, April 2003

We calculate the photonuclear production of heavy quarks in ultraperipheral heavy ion collisions. The integrated cross section and the rapidity distribution are computed employing sound high energy QCD formalisms as the collinear and semihard approaches as well as the saturation model. In particular, the color glass condensate (CGC) formalism is also considered using a simple phenomenological parameterization for the color field correlator in the medium, which allow us to obtain more reliable estimates for charm and bottom production at LHC energies., Comment: 15 pages, 2 figures. Extended version to be published in Eur. Phys. J. C

We calculate the nucleon and nuclear photoproduction cross sections for heavy quarks within the $k_{\perp}$-factorization formalism, considering the current high energy approaches which include nuclear and saturation effects. Our results demonstrate that a future experimental analysis of this process would allow to constraint the QCD dynamics at high energies., Comment: 10 pages, 2 figures. Version to be published in Eur. Phys. J. C

We show that the cross section for inclusive charm production exhibits geometric scaling in a large range of photon virtualities. In the HERA kinematic domain the saturation momentum $Q_{sat}^2(x)$ stays below the hard scale $\mu_c^2=4m_c^2$, implying charm production probing mostly the color transparency regime and unitarization effects being almost negligible. We derive our results considering two saturation models which are able to describe the DESY ep collider HERA data for the proton structure function at small values of the Bjorken variable $x$. A striking feature is the scaling on $\tau=Q_2^2/Q_{sat}^2(x)$ above saturation limit, corroborating recent theoretical studies., Comment: 4 pages, 2 figures. Version to be published in Physical Review Letters

We calculate the nuclear inclusive and diffractive cross sections for heavy quark photoproduction within a phenomenological saturation approach. The nuclear cross section is obtained by the extension of the saturation model through Glauber-Gribov formalism. We predict large nuclear heavy quark cross section at LHC energies., Comment: 14 pages, 6 figures. Version to be published in Eur. Phys. J. C

We perform an adjust to the most recent structure function data, considering the QCD dipole picture applied to ep scattering. The structure function F2 at small x and intermediate Q2 can be described by the model containing an economical number of free-parameters, which encodes the hard Pomeron physics. The longitudinal structure function and the gluon distribution are predicted without further adjustments. The data description is effective, whereas a resummed next-to-leading level analysis is deserved., Comment: 18 pages, 6 figures. Version to be published in Eur. Phys. J. A

We perform a global fit to the inclusive structure function considering a QCD inspired model describing the ep scattering. In lines of a two Pomeron approach, the structure function F_2 has a hard piece given by the model and the remaining soft contributions: the soft Pomeron and non-singlet content. We have investigated several choices for the soft Pomeron and its implication in the data description. In particular, we carefully estimated the relative role of the hard and the soft contributions in a large span of x and Q^2., Comment: 14 pages, 3 figures. To be published in Eur. Phys. J. A

The double meson production in ultraperipheral heavy ions collisions is addressed, focusing on the particular case of rho-J/Psi from two-photon reactions. The cross section at photon level is obtained using distinct parameterizations for the gluon distribution on the light meson. The resulting estimates for the nuclear case are presented and discussed. As a by product, we estimate the double rho production cross section using the Pomeron-exchange factorization relations., Comment: 12 pages, 5 figures. Version to be published in n Eur. Phys. J. C

We study the influence of unitarity corrections on the Drell-Yan transverse momentum distribution within the color dipole approach. These unitarity corrections are implemented through the multiple scattering Glauber-Mueller approach, which is contrasted with a phenomenological saturation model. The process is analyzed for the center of mass energies of the Relativistic Heavy Ion Collider (RHIC, $\sqrt{s}=500$ GeV) and of the Large Hadron Collider (LHC, $\sqrt{s}=14$ TeV). In addition, the results are extrapolated down to current energies of proton-proton collisions, where non-asymptotic corrections to the dipole approach are needed. It is also shown that in the absence of saturation, the dipole approach can be related to the QCD Compton process., Comment: 17 pages, 6 figures, revtex4 style. Version to be published in Phys. Rev. D

We investigate the deeply virtual Compton scattering (DVCS) in the color dipole approach, implementing the dipole cross section through the saturation model, which interpolates successfully between soft and hard regimes. The imaginary and real part of the DVCS amplitude are obtained and the results are compared to the available data., Comment: 12 pages - Vers.2. Accepted by EJP

The heavy quark production in ultraperipheral heavy ion collisions is investigated, in particular we focus on the results from the coherent interactions given by the two-photon process. One addresses the heavy quark total cross sections at photon level considering the saturation model and the BFKL dynamics in the color dipole picture. The corresponding cross sections at nuclear level are presented. It is verified that the QCD dynamics implies an enhancement of the cross section in comparison with previous calculations., Comment: 16 pages, 7 figures. Version to be published in Eur. Phys. J. C

In this contribution we report on the calculations of heavy-quark photoproduction using the semihard approach, emphasizing the results obtained with the phenomenological saturation model., Comment: 4 pages, 1 figure. Contribution to the Workshop on Low x Physics, Antwerpen (Belgium), 16-19 Sept. 2002, and to the Brazilian National Meeting on Particle Physics and Fields, Aguas de Lindoia (Brazil), 15-19 Oct. 2002

The contribution of the QCD Pomeron to the process AA -> AA J/Psi J/Psi is discussed. We focus on the photon-photon collision, with the quasi-real photon coming from the Weizsacker - Williams spectrum of the nuclei. We calculate the cross section for this process considering the solution of the LLA BFKL equation at zero momentum transfer using a small-t approximation for the differential cross section of the subprocess. Furthermore, the impact of non-leading corrections to the BFKL equation is also analyzed. In both cases the cross section is found to increase with the energy, predicting considerable values for the LHC energies. Moreover, we compare our results with the Born two-gluon approximation, which is energy independent at the photon level. Our results indicate that the experimental analyzes of this process can be useful to discriminate the QCD dynamics at high energies., Comment: 13 pages, 4 figures. Version to be published in Eur. Phys. J. C

We report on the extension of the data fitting considering the QCD inspired model based on the summation of gluon ladders applied to the $ep$ scattering. In lines of a two Pomeron approach, the structure function $F_2$ has a hard piece given by the model and the remaining soft contribution: a soft Pomeron and non-singlet content. In this contribution, we carefully estimate the relative role of the hard and the soft pieces from a global fit in a large span of $x$ and $Q^2$., Comment: 10 pages, 3 figures, uses crckapb.sty. To appear in the proceedings of Diffraction 2002: Second International "Cetraro" Workshop and NATO Advanced Research Workshop

We investigate the heavy quark photoproduction based on the k_T factorization approach, focusing on the results from the saturation model. The deviations in the results using the unintegrated gluon distribution considering the saturation model and the derivative of the collinear gluon distribution are analysed. Total cross sections and p_T distributions are analysed in detail, setting the deviations between the color dipole approximation and the complete semihard approach., Comment: 18 pages, 7 figures, minor changes, references added. Accepted for publication in Phys. Rev. D

We report on the results obtained in the study of the parton saturation effects, taken into account through the multiscattering Glauber-Mueller approach, applied to the Drell-Yan (DY) process described in the color dipole picture. As a main result, one shows that those effects play an important role in the estimates of the DY differential cross section atRHIC energies., Comment: To appear in the proceedings of the VIII International Workshop on Hadron Physics 2002

We study in detail the main features of the unitarized Regge model (CFKS), recently proposed to describe the small-$Q^2$ domain. It takes into account a two-component description with two types of unitarized contributions: one is the multiple Pomeron exchanges contribution, interacting with the large dipole size configurations, and the other one consists on a unitarized dipole cross section, describing the interaction with the small size dipoles. We compare the resulting dipole cross section to that from the saturation model (GBW)., Comment: 4 pages, latex, 2 figures. To appear in the proceedings of the XXXVIIth Rencontres de Moriond

We have studied the color dipole picture for the description of the deep inelastic process, mainly the structure functions which are driven directly by the gluon distribution. Estimates for those functions are obtained using the effective dipole cross section given by the Glauber-Mueller approach in QCD, encoding the corrections due to the unitarity effects associated with the saturation phenomenon. Frame invariance is verified in the calculations of the observables when analysing the experimental data., Comment: 9 pages, 4 figures, uses aip style . Talk presented by M.B. Gay Ducati at the Pan American Advanced Studies Institute (PASI2002), January 7-18, 2002

Electroproduction in deep inelastic scattering at HERA is studied in a model considering a finite sum of gluon ladders, associated with a truncation of the BFKL series. The approach contains the bare two gluon exchange and both one and two rungs contributions. The model is fitted to the data on the inclusive structure function F_2(x,Q^2) in the region x<0.025 and 0.045

The unitarity corrections effects encoded in the Glauber-Mueller approach are taken into account to calculate the differential cross sections in the Drell-Yan process in the rest frame. A detailed study of the Drell-Yan process in terms of the $\gamma^{*}q$ transverse separation and the color dipole size, as well as the effective dipole cross section is performed and compared with the available small $x$ data. Estimates for the Drell-Yan cross section at RHIC energies are presented and discussed., Comment: 31 pages, 8 figures. Version to be published in Phys. Rev. D

The logarithmic slope of the diffractive structure function is a potential observable scanning the hard and soft contributions in diffraction, allowing to disentangle the QCD dynamics. We report our calculations concerning this quantity, in particular the estimates emerging from the saturation model applied to diffraction dissociation., Comment: 4 pages, 1 figure (in eps) talk given at XXXI International Symposium on Multiparticle Dynamics, Sep. 1-7, 2001, Datong China URL http://ismd31.ccnu.edu.cn/

We study the dipole picture for the description of the deep inelastic scattering, focusing on the structure functions which are driven directly by the gluon distribution. One performs estimates using the effective dipole cross section given by the Glauber-Mueller approach in QCD, which encodes the corrections due to the unitarity effects associated with the saturation phenomenon. We also address issues about frame invariance of the calculations when analysing the observables., Comment: 16 pages, 8 figures. Version to be published in Phys. Rev. D

We study in detail the main features of the unitarized Regge model (CFKS), recently proposed to describe the small-$Q^2$ domain. It takes into account a two-component description with two types of unitarized contributions: one is the multiple pomeron exchange contribution, interacting with the large dipole configurations, and the other one consists of a unitarized dipole cross section, describing the interaction with the small size dipoles. We analyze the ratio between soft and hard pieces as a function of the virtuality, and also compare the resulting dipole cross section to that from the saturation model. Diffraction dissociation is also considered, showing the scaling violations in diffractive DIS and estimating the corresponding logarithmic slope., Comment: 14 pages, 5 postscript figures. Version to be published in Eur. Phys. J. C

We report our calculations on the logarithmic slope of the diffractive structure function F_2^D considering distinct approaches coming from both the pQCD and the Regge descriptions of diffractive DIS. Such a quantity is a potential observable to discriminate between pQCD and Regge domains and allows to disentangle the underlying dynamics., Comment: 8 pages, 3 figures, style elsart.cls. Talk presented by M.B. Gay Ducati at the IXth Blois Workshop, Pruhonice near Prague, June 9-15, 2001