arXiv subjects

V. P. Goncalves

Publications and source records attributed to V. P. Goncalves.

At least 91 records · Page 5Linked to original sources

arXiv2015

Constraining the photon flux in two-photon processes at the LHC

In this paper we propose the study of the $W^+W^-$ and $μ^+μ^-$ production by two-photon interactions in $pp$ collisions at LHC energies to constrain the photon flux associated to an ultrarelativistic proton. We consider the current parametrizations for the photon distribution of the proton and estimate the effective photon - photon luminosities for elastic, semielastic and inelastic processes. Moreover, we present predictions for the rapidity and invariant mass distributions for the two-photon production of $W^+W^-$ and $μ^+μ^-$ in $γγ$ interactions at LHC energies. We demonstrate that the semielastic and inelastic predictions are strongly dependent on the description of the inelastic photon flux, and that the relative contribution of the different processes depends on the invariant mass of the final state. Our results implies that a dedicated experimental analysis of the two-photon production of $W^+W^-$ and $μ^+μ^-$ with the tagging of one of the protons in the final state can be useful to constrain the magnitude of the inelastic component of the photon distribution.

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arXiv2015

Double $J/ψ$ production in central diffractive processes at the LHC

In this paper we study the double $J/ψ$ production in central diffractive processes considering the Resolved Pomeron model. Based on the nonrelativistic QCD (NRQCD) factorization formalism for the quarkonium production mechanism we estimate the rapidity and transverse momentum dependence of the cross section for the double $J/ψ$ production in diffractive processes at LHC energies. The contributions of the color-singlet and color-octet channels are estimated and predictions for the total cross sections in the kinematical regions of the LHC experiments are also presented. Our results demonstrate that the contribution of central diffractive processes is not negligible and that its study can be useful to test the Resolved Pomeron model.

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arXiv2015

Deeply virtual Compton scattering at small-$x$ in future Electron - Ion Colliders

The study of exclusive processes in the future electron-ion ($eA$) colliders will be an important tool to investigate the QCD dynamics at high energies as they are in general driven by the gluon content of the target which is strongly subject to parton saturation effects. In this paper we compute the coherent and incoherent cross sections for the deeply virtual Compton scattering (DVCS) process relying on the color dipole approach and considering different models for the dipole - proton scattering amplitude. The dependencies of the cross sections with the energy, photon virtuality, nuclear mass number and squared momentum transfer are analysed in detail. We demonstrate that the ratio between the incoherent and coherent cross sections decreases at smaller values of $Q^2$ and increases at smaller values of $A$. We show that the coherent cross section dominates at small $t$ and exhibits the typical diffractive pattern, with the number of dips in the range $|t| \le 0.3$ GeV$^2$ increasing with the mass atomic number. Our results indicate that the position of the dips are independent of the model used to treat the dipole - proton interaction as well as of the center-of-mass energy.

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arXiv2015

Double vector meson production in the International Linear Collider

In this paper we study double vector meson production in $γγ$ interactions at high energies and, using the color dipole picture, estimate the main observables which can be probed at the International Linear Collider (ILC). The total $γ(Q_1^2) + γ(Q_2^2) \rightarrow V_1 + V_2$ cross-sections for $V_i = ρ$, $ϕ$, $J/ψ$ and $Υ$ are computed and the energy and virtuality dependencies are studied in detail. Our results demonstrate that the experimental analysis of this process is feasible at the ILC and it can be useful to constrain the QCD dynamics at high energies.

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arXiv2015

$η_c$ production in photon - induced interactions at the AFTER@LHC experiment as a probe of the Odderon

One of the open questions of the strong interaction theory is the existence of the Odderon, which is an unambiguous prediction of Quantum Chromodynamics, but still not confirmed experimentally. An alternative to probe the Odderon is the exclusive $η_c$ photoproduction in hadronic collisions. As the Pomeron exchange cannot contribute to this process, its observation would indicate the existence of the Odderon. In this paper we estimate the $η_c$ production in photon - induced interactions in hadronic collisions at the AFTER@LHC experiment. We demonstrate that the experimental analysis of this process is feasible in the AFTER@LHC experiment and that the observation of the $η_c$ production in nuclear collisions is a unambiguous signature of the Odderon.

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arXiv2015

Probing the photon flux in the diffractive quarkonium photoproduction at LHC

In this paper we propose the study of the diffractive quarkonium photoproduction in $pp$ collisions at LHC energies to probe the photon flux associated to a ultrarelativistic proton. The total photon distribution is expected to be given in terms of the elastic and inelastic components. Distinctly from the elastic photon component which can be determined from the elastic form factors, the magnitude of the inelastic component still is an open question. We consider the current parametrizations for the photon distribution of a proton and estimate the rapidity distributions and total cross sections for the production of $J/Ψ$, $Ψ^{\prime}$ and $Υ$ at LHC energies. We demonstrate that the predictions associated to the inelastic contribution are of the same order than those associated to the elastic one. Our results implies that a dedicated experimental analysis of diffractive quarkonium photoproduction with the tagging of the two protons in the final state can be useful to constrain the magnitude of the inelastic component of the photon distribution.

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arXiv2015

Exclusive $Υ$ photoproduction in hadronic collisions at CERN LHC energies

The exclusive $Υ$ photoproduction in proton-proton and proton - nucleus collisions at LHC energies is investigated using the color dipole formalism and considering different models for the $Υ$ wave function and forward dipole - target scattering amplitude. Our goal is to update the color dipole predictions and estimate the theoretical uncertainty present in these predictions. We present predictions for the kinematical ranges probed by the ALICE, CMS and LHCb Collaborations.

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arXiv2015

Probing the dilaton in central exclusive processes at the LHC

The existence of a dilaton as a pseudo-Nambu-Goldstone boson in spontaneous breaking of scale symmetry is predicted in beyond standard model theories in which electroweak symmetry is broken via strongly coupled conformal dynamics. Such a particle is expected to have a mass below the conformal symmetry breaking scale $f$ and couplings to standard model particles similar to those of the SM Higgs boson. In this paper we estimate, for the first time, the dilaton production in exclusive processes considering Pomeron - Pomeron ($\pom \pom$) and photon - photon ($γγ$) interactions, which are characterized by two rapidity gaps and intact hadrons in the final state. Our results indicate that if the dilaton is massive ($M_χ \ge 2 M_W$), the study of dilaton production by $\pom \pom$ interactions in $pp$ collisions can be useful to determine its mass and the conformal energy scale.

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arXiv2014

Inclusive gauge boson production in the color dipole formalism

The inclusive production of the gauge bosons $W^{\pm}$ and $Z^0$ is studied within the color dipole formalism. Gluon saturation effects associated to non-linear corrections to the QCD dynamics, which are expected to contribute at high energies, are naturally included in such formalism. We estimate the contribution of these effects at LHC energies and compare our results with the next-to-next-to-leading order collinear predictions. A comparison with the current experimental data is performed and predictions for higher energies are presented.

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arXiv2014

Estimating non-linear QCD effects in ultrahigh energy neutrino events at IceCube

The number of ultrahigh energy events at IceCube is estimated, for the first time, taking into account non-linear QCD effects in the neutrino - hadron cross section. We assume that the extragalactic neutrino flux is given by $Φ_ν(E_ν)=Φ_{0}E^{-2}_ν$ and estimate the neutrino - hadron cross section using the dipole approach and a phenomenological model for the dipole - hadron cross section based on non-linear QCD dynamics. We demonstrate that the non-linear prediction is able to describe the current IceCube data and that the magnitude of the non-linear effects is larger than 20 % for visible energies of order of 2 PeV and increases with the neutrino energy. Our main conclusion is that the non-linear QCD effects are non-negligible and should be taken into account in the analysis of the number of ultrahigh energy events.

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arXiv2014

Probing gluon number fluctuation effects in future electron-hadron colliders

The description of the QCD dynamics in the kinematical range which will be probed in the future electron - hadron colliders is still an open question. Although phenomenological studies indicate that the gluon number fluctuations, which are related to discreteness in the QCD evolution, are negligible at HERA, the magnitude of these effects for the next generation of colliders still should be estimated. In this paper we investigate inclusive and diffractive $ep$ observables considering a model for the physical scattering amplitude which describes the HERA data. Moreover, we estimate, for the first time, the contribution of the fluctuation effects for the nuclear structure functions. Our results indicate that the study of these observables in the future colliders can be useful to constrain the presence of gluon number fluctuations.

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arXiv2014

Investigation of diffractive photoproduction of $J/Ψ$ in hadronic collisions

In this work we study the diffractive photoproduction of $J/Ψ$ in proton-proton, proton - nucleus and nucleus - nucleus collisions at LHC energies using the color dipole formalism and different models for the forward dipole - target scattering amplitude. Our goal is to estimate the theoretical uncertainty present in the current predictions in the literature. Our results are compared with the experimental data and predictions for higher energies are presented.

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arXiv2014

Heavy Quark Production in Ultra High Energy Cosmic Ray Interactions

In this paper we present a comprehensive study of the heavy quark production in ultra high energy cosmic ray interactions in the atmosphere considering that the primary cosmic ray can be either a photon, neutrino or a proton. The analysis is performed using a unified framework -- the dipole formalism --- and the saturation effects, associated to the physical process of parton recombination, are taken into account. We demonstrate that the contribution of heavy quarks for cosmic ray interactions is in general non-negligible and can be dominant depending of the process considered. Moreover, our results indicate that new dynamical mechanisms should be included in order to obtain reliable predictions for the heavy quark production in $pp$ collisions at ultra high cosmic ray energies.

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arXiv2014

Diffractive $Z$ boson pair production at LHC in the large extra dimensions scenario

In this paper we study the diffractive $Z$ boson pair production mediated by the Kaluza-Klein graviton in the large extra dimensions scenario at the CERN Large Hadron Collider energies. Considering the Durham model we estimate the total cross section for the central inclusive and exclusive diffractive production of a $Z$ boson pair in $pp/pPb/PbPb$ collisions. Our results indicate that the experimental analysis of the central inclusive production in $pp$ collisions is feasible at CERN LHC.

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arXiv2014

Deciphering charmoniumlike exotic states in photon - hadron interactions at RHIC and LHC energies

In this paper we propose the study of the photoproduction of charmoniumlike states in $pp$ collisions at RHIC and LHC energies and estimate the rapidity distribution and total cross sections for the production of the exotic hadrons $Y(3940)$, $X(3915)$, $Z(4430)$ and $Z_c(3900)$. We demonstrate that the experimental analysis of this process can provide complementary and independent checks on these states, and help to understand their underlying nature.

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arXiv2014

Baryon stopping in the Color Glass Condensate formalism: A phenomenological study

The net-baryon production at forward rapidities is investigated considering the Color Glass Condensate formalism. We assume that at large energies the coherence of the projectile quarks is lost and that the leading baryon production mechanism changes from recombination to independent fragmentation. The phenomenological implications for net-baryon production in $pp/pA/AA$ collisions are analysed and predictions for LHC energies are presented.

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arXiv2013

Single and double diffractive prompt photon production at the LHC

In this contribution we study for the first time the prompt photon production in single and double diffractive processes considering the resolved Pomeron model. We estimate the rapidity and transverse momentum dependence of the cross section for the production of two photons and of a photon and a jet. We show that these processes are sensitive to the pomeron structure. In contrast with the dijet and heavy quark production, which are dominated by gluon-gluon interactions, in prompt photon production, Compton like processes are dominant for single photon plus jet events. This gives a unique oportunity to constrain the quark distribution in the Pomeron. The results are obtained for the LHC energy.

hep-ph↗

arXiv2013

Diffractive photon production at the LHC

In this paper we study the photon production in single and double diffractive processes considering the Resolved Pomeron model. We estimate the rapidity and transverse momentum dependence of the cross section for the diffractive double photon and photon+jet production. A comparison with the inclusive production is presented. We predict large values for the total cross sections, which makes the experimental analysis of these observables feasible at LHC energies.

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