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M. V. T. Machado

Publications and source records attributed to M. V. T. Machado.

At least 73 records · Page 4Linked to original sources

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 $J/Ψ$ and $ρ$ cross sections at RHIC energies.

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Exclusive glueball production in high energy nucleus-nucleus collisions

The cross sections for the glueball candidates production in quasi-real photon-photon collisions and on central diffraction processes, i.e. double Pomeron exchange, in heavy ion interactions at RHIC and LHC are computed. The rates for these distinct production channels are compared and they may be a fruitful approach to the investigation of glueballs.

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Charm and bottom production in inclusive double Pomeron exchange in heavy ion collisions at the LHC

The inclusive double Pomeron exchange cross section for heavy quark pair production is calculated for nucleus-nucleus collisions at the LHC. The present estimate is based on hard diffractive factorization, corrected by absorptive corrections and nuclear effects. The theoretical uncertainties for nuclear collisions are investigated and a comparison to other approaches is presented. The production channels producing a similar final state configuration are discussed as well.

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Non-linear QCD dynamics and exclusive production

In this contribution we analyse the cross sections for the exclusive vector meson production as well as the deeply virtual Compton scattering (DVCS) relying on the color dipole approach and considering the numerical solution of the Balitsky-Kovchegov equation including running coupling corrections. Comparisons to DESY-HERA data on exclusive processes and predictions to the Large Hadron Electron Collider, LHeC, are presented.

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Photon plus heavy quark production in high energy collisions within the target rest frame formalism

We apply the target rest frame formalism to photon + heavy quark production cross section in hadronic collisions at high energies. We investigate the dependence of the production cross section on the photon and quark rapidities and transverse momenta. It is shown that the photon transverse momentum spectrum is a sensitive probe of color dipole scattering amplitude. The theoretical results are compared to Tevatron measurements of the differential γ+ c + X and γ+ b + X production cross sections at 1.96 TeV. An analysis for proton-proton and proton-lead collisions at the LHC regime is also performed.

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Estimate of the single diffractive heavy quark production in heavy ion collisions at the CERN-LHC

The single diffractive cross section for heavy quarks production is calculated in next-no-leading order (NLO) in nucleus-nucleus collisions. Such processes are expected to occur at the LHC. We start using the hard diffractive factorization formalism, taking into account the recent experimental parameterization for the Pomeron Structure Function (DPDF). Absorptive corrections are accounted by the multiple Pomeron contributions considering a gap survival probability, where its theoretical uncertainty for nuclear collisions is discussed. We estimate the diffractive ratios for single diffraction process in nuclear coherent/incoherent collisions at the LHC.

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Quarkonium plus prompt-photon associated hadroproduction and nuclear shadowing

The quarkonium hadroproduction in association with a photon at high energies provides a probe of the dynamics of the strong interactions as it is dependent on the nuclear gluon distribution. Therefore, it could be used to constrain the behavior of the nuclear gluon distribution in proton-nucleus and nucleus-nucleus collisions. Such processes are useful to single out the magnitude of the shadowing/antishadowing effects in the nuclear parton densities. In this work we investigate the influence of nuclear effects in the production of JPsi + photon and Upsilon + photon and estimate the transverse momentum dependence of the nuclear modification factors. The theoretical framework considered in the JPsi (Upsilon) production associated with a direct photon at the hadron collider is the non-relativistic QCD (NRQCD) factorization formalism.

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Non-linear QCD dynamics and exclusive production in $ep$ collisions

The exclusive processes in electron-proton ($ep$) interactions are an important tool to investigate the QCD dynamics at high energies as they are in general driven by the gluon content of proton which is strongly subject to parton saturation effects. In this paper we compute the cross sections for the exclusive vector meson production as well as the deeply virtual Compton scattering (DVCS) relying on the color dipole approach and considering the numerical solution of the Balitsky-Kovchegov equation including running coupling corrections. We show that the small-$x$ evolution given by this evolution equation is able to describe the DESY-HERA data and is relevant for the physics of the exclusive observables in future electron-proton colliders and in photoproduction processes to be measured in coherent interactions at the LHC.

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Heavy quark photoproduction in $pp$ coherent interactions at LHC

In this work we analyse the possibility of constraining the QCD dynamics at high energies studying the heavy quark photoproduction at LHC in coherent interactions. The rapidity distribution and total cross section for charm and bottom production are estimated using three different phenomenological saturation models which successfully describe the HERA data. Our results indicate that the experimental study of the inclusive heavy quark photoproduction can be very useful to discriminate between the classical and quantum versions of the Color Glass Condensate (CGC) formalism.

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A simple model for the nuclear unintegrated gluon distribution

The solution of non-linear evolution equations for dense nuclear gluon density has been suggested as one of the relevant mechanisms of pA and AA collisions at collider energies. Here we study a simple parameterization for the unintegrated gluon distribution using the knowledge of asymptotic solutions of the Balitsky-Kovchegov equation, describing high-energy QCD in the presence of saturation effects. A satisfactory description of nuclear shadowing at small-x is obtained and it allows us to understand the qualitative behavior shown by data.

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Photoproduction of $ρ^0$ 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 $ρ$ 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.

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Diffractive quarkonium production in association with a photon at the LHC

The rates for diffractive quarkonium plus prompt-photon associated production at the LHC are estimated. The theoretical framework considered in the J/Psi (or Upsilon) production associated with a direct photon at the hadron collider is the non-relativistic QCD (NRQCD) factorization formalism. The corresponding single diffractive cross section is computed based on the hard diffractive scattering factorization supplemented by absorptive corrections. Such processes are sensitive to the gluon content of the Pomeron at small Bjorken-x and they may also be a good place to test the different available mechanisms for quarkonium production at hadron colliders.

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Nuclear DVCS within the high energy QCD color dipole formalism

In this contribution, we present a study of the coherent and incoherent nuclear DVCS process in the small-$x$ regime within the color dipole formalism. Predictions for the nuclear DVCS cross section at photon level in the collider kinematics are presented.

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Heavy Quark Photoproduction in Coherent Interactions at High Energies

We calculate the inclusive and diffractive photoproduction of heavy quarks in proton-proton collisions at Tevatron and LHC energies, where the photon reaches energies larger than those ones accessible at DESY-HERA. The integrated cross section and the rapidity distributions for charm and bottom production are computed within the color dipole picture employing three phenomenological saturation models based on the Color Glass Condensate formalism. Our results demonstrate that the experimental analyzes of these reactions is feasible and that the cross sections are sensitive to the underlying parton dynamics.

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Exclusive vector meson production in electron-ion collisions

We calculate the nuclear cross section for coherent and incoherent vector meson production within the QCD color dipole picture, including saturation effects. Theoretical estimates for scattering on both light and heavy nuclei are given over a wide range of energy.

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Diffractive photoproduction of Z^0 bosons in coherent interactions at CERN-LHC

The exclusive $Z^0$ photoproduction at high energies in $γp (A)$, $p p$ and $AA$ collisions is investigate within the color dipole formalism. We generalize the description of the deeply virtual compton scattering (DVCS) process, which describe quite well the HERA data, for the production of $Z^0$ bosons and estimate the total cross section for the exclusive process $γ^* h\to Z^0 h$ ($h=p,A$) for different energies, photon virtualities and atomic numbers. As hadrons at collider energies are a source of Weizsäcker - Williams photons, we consider electromagnetic interactions in hadron-hadron collisions at Tevatron and LHC energies and estimate the rapidity distribution and total cross section for $Z^0$ production in the $h h\to h Z^0 h$ process. This is the first estimation for such a process in literature. It can allow us to study, for instance, the physics of hadronic $Z^0$ decays in a clean environment characterized by two rapidity gaps. Our results indicate that the experimental analyzes of this process could be feasible in $pp$ but the physics scenario for $AA$ collisions is not promising.

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Neutral current neutrino-nucleus interactions at high energies

We present a QCD analysis of the neutral current neutrino-nucleus interaction at the small-x region using the color dipole formalism. This phenomenological approach is quite successful in describing experimental results in deep inelastic ep scattering and charged current neutrino-nucleus interactions at high energies. We present theoretical predictions for the relevant structure functions and the corresponding implications for the total NC neutrino cross section.

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