arXiv subjects

V. P. Goncalves

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

At least 73 records · Page 4Linked to original sources

arXiv2017

Photon and Pomeron -- induced production of Dijets in $pp$, $pA$ and $AA$ collisions

In this paper we present a detailed comparison of the dijet production by photon -- photon, photon -- pomeron and pomeron -- pomeron interactions in $pp$, $pA$ and ${\rm AA}$ collisions at the LHC energy. The transverse momentum, pseudo -- rapidity and angular dependencies of the cross sections are calculated at LHC energy using the Forward Physics Monte Carlo (FPMC), which allows to obtain realistic predictions for the dijet production with two leading intact hadrons. We obtain that $γ\pom$ channel is dominant at forward rapidities in $pp$ collisions and in the full kinematical range in the nuclear collisions of heavy nuclei. Our results indicate that the analysis of dijet production at the LHC can be useful to test the Resolved Pomeron model as well as to constrain the magnitude of the absorption effects.

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arXiv2017

Investigating the influence of diffractive interactions on ultra - high energy extensive air showers

The understanding of the basic properties of the ultra - high energy extensive air showers is strongly dependent on the description of the hadronic interactions in a energy range beyond that probed by the LHC. One of the uncertainties present in the modeling of the air showers is the treatment of diffractive interactions, which are dominated by non - perturbative physics and usually described by phenomenological models. These interactions are expect to affect the development of the air showers, since they provide a way of transporting substantial amounts of energy deep in the atmosphere, modifying the global characteristics of the shower profile. In this paper we investigate the impact of the diffractive interactions in the observables that can be measured in hadronic collisions at high energies and ultra - high energy cosmic ray interactions. We consider three distinct phenomenological models for the treatment of diffractive physics and estimate the influence of these interactions on the elasticity, number of secondaries, longitudinal air shower profiles and muon densities for proton - air and iron - air collisions at different primary energies. Our results demonstrate that the diffractive events has a non - negligible effect on the observables and that the distinct approaches for these interactions, present in the phenomenological models, are an important source of theoretical uncertainty for the description of the extensive air showers.

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arXiv2017

Investigating the impact of the gluon saturation effects on the momentum transfer distributions for the exclusive vector meson photoproduction in hadronic collisions

The exclusive vector meson production cross section is one of the most promising observables to probe the high energy regime of the QCD dynamics. In particular, the squared momentum transfer ($t$) distributions are an important source of information about the spatial distribution of the gluons in the hadron and about fluctuations of the color fields. In this paper we complement previous studies on exclusive vector meson photoproduction in hadronic collisions presenting a comprehensive analysis of the $t$ - spectrum measured in exclusive $ρ$, $ϕ$ and $J/Ψ$ photoproduction in $pp$ and $PbPb$ collisions at the LHC. We compute the differential cross sections taking into account gluon saturation effects and compare the predictions with those obtained in the linear regime of the QCD dynamics. Our results show that gluon saturation suppresses the magnitude of the cross sections and shifts the position of the dips towards smaller values of $t$.

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arXiv2016

Exclusive heavy vector meson photoproduction in hadronic collisions at the LHC: predictions of the Color Glass Condensate model for Run 2 energies

In this letter we update our predictions for exclusive $J/Ψ$ and $Υ$ photoproduction in proton-proton and nucleus - nucleus collisions at the Run 2 LHC energies obtained with the color dipole formalism and considering the impact parameter Color Glass Condensate model (bCGC) for the forward dipole - target scattering amplitude. A comparison with the LHCb data on rapidity distributions and photon - hadron cross sections is presented. Our results demonstrate that the current data can be quite well described by the bCGC model, which takes into account nonlinear effects in the QCD dynamics and reproduces the very precise HERA data, without introducing any additional effect or free parameter.

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arXiv2016

Production of exotic charmonium in $γγ$ interactions at hadronic colliders

In this paper we investigate the Exotic Charmonium (EC) production in $γγ$ interactions present in proton-proton, proton-nucleus and nucleus-nucleus collisions at the CERN Large Hadron Collider (LHC) energies as well as for the proposed energies of the Future Circular Collider (FCC). Our results demonstrate that the experimental study of these processes is feasible and can be used to constrain the theoretical decay widths and shed some light on the configuration of the considered multiquark states.

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arXiv2016

Probing the diffractive production of gauge bosons at forward rapidities

The gauge boson production at forward rapidities in single diffractive events at the LHC is investigated considering $pp$ collisions at $\sqrt{s} =$ 8 and 13 TeV. The impact of gap survival effects is analysed using two different models for the soft rescattering contributions. We demonstrate that using the Forward Shower Counter Project at LHCb -- HERSCHEL, together with the Vertex Locator -- VELO, it is possible to discriminate diffractive production of the gauge bosons $W$ and $Z$ from the non-diffractive processes and studies of the Pomeron structure and diffraction phenomenology are feasible. Moreover, we show that the analysis of this process can be useful to constrain the modelling of the gap survival effects.

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arXiv2016

Exclusive vector meson photoproduction at the LHC and the FCC: A closer look on the final state

Over the past years the LHC experiments have reported experimental evidences for processes associated to photon-photon and photon-hadron interactions, showing their potential to investigate the production of low- and high-mass systems in exclusive events. In the particular case of the photoproduction of vector mesons, the experimental study of this final state is expected to shed light on the description of the QCD dynamics at small values of the Bjorken-$x$ variable. In this paper we extend previous studies for the exclusive $J/Ψ$ and $Υ$ photoproduction in $pp$ collisions based on the nonlinear QCD dynamics by performing a detailed study of the final state distributions that can be measured experimentally at the LHC and at the Future Circular Collider. Predictions for the rapidity and transverse momentum distributions of the vector mesons and of final-state dimuons are presented for $pp$ collisions at $\sqrt{s} =$ 7, 13, and 100 TeV.

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arXiv2016

Testing the running coupling $k_{T}$-factorization formula for the inclusive gluon production

The inclusive gluon production at midrapidities is described in the Color Glass Condensate formalism using the $k_T$ - factorization formula, which was derived at fixed coupling constant considering the scattering of a dilute system of partons with a dense one. Recent analysis demonstrated that this approach provides a satisfactory description of the experimental data for the inclusive hadron production in $pp/pA/AA$ collisions. However, these studies are based on the fixed coupling $k_T$ - factorization formula, which does not take into account the running coupling corrections, which are important to set the scales present in the cross section. In this paper we consider the running coupling corrected $k_T$ - factorization formula conjectured some years ago and investigate the impact of the running coupling corrections on the observables. In particular, the pseudorapidity distributions and charged hadrons multiplicity are calculated considering $pp$, $dAu/pPb$ and $AuAu/PbPb$ collisions at RHIC and LHC energies. We compare the corrected running coupling predictions with those obtained using the original $k_T$ - factorization assuming a fixed coupling or a prescription for the inclusion of the running of the coupling. Considering the Kharzeev - Levin - Nardi unintegrated gluon distribution and a simplified model for the nuclear geometry, we demonstrate that the distinct predictions are similar for the pseudorapidity distributions in $pp/pA/AA$ collisions and for the charged hadrons multiplicity in $pp/pA$ collisions. On the other hand, the running coupling corrected $k_T$ - factorization formula predicts a smoother energy dependence for $dN/dη$ in $AA$ collisions.

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arXiv2016

Diffractive $ρ$ production at small $x$ in future Electron - Ion Colliders

The future Electron - Ion ($eA$) Collider is expected to probe the high energy regime of the QCD dynamics, with the exclusive vector meson production cross section being one of the most promising observables. In this paper we complement previous studies of exclusive processes presenting a comprehensive analysis of diffractive $ρ$ production at small $x$. We compute the coherent and incoherent cross sections taking into account non-linear QCD dynamical effects and considering different models for the dipole - proton scattering amplitude and for the vector meson wave function. The dependence of these cross sections with the energy, photon virtuality, nuclear mass number and squared momentum transfer is analysed in detail. Moreover, we compare the non-linear predictions with those obtained in the linear regime. Finally, we also estimate the exclusive photon, $J/Ψ$ and $ϕ$ production and compare with the results obtained for $ρ$ production. Our results demonstrate that the analysis of diffractive $ρ$ production in future electron - ion colliders will be important to understand the non-linear QCD dynamics.

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arXiv2016

Double vector meson production in photon - hadron interactions at hadronic colliders

In this paper we analyse the double vector meson production in photon -- hadron ($γh$) interactions at $pp/pA/AA$ collisions and present predictions for the $ρρ$, $J/ΨJ/Ψ$ and $ρJ/Ψ$ production considering the double scattering mechanism. We estimate the total cross sections and rapidity distributions at LHC energies and compare our results with the predictions for the double vector meson production in $γγ$ interactions at hadronic colliders. We present predictions for the different rapidity ranges probed by the ALICE, ATLAS, CMS and LHCb Collaborations. Our results demonstrate that the $ρρ$ and $J/ΨJ/Ψ$ production in $PbPb$ collisions is dominated by the double scattering mechanism, while the two - photon mechanism dominates in $pp$ collisions. Moreover, our results indicate that the analysis of the $ρJ/Ψ$ production at LHC can be useful to constrain the double scattering mechanism.

hep-ph↗

arXiv2016

Exclusive vector meson production with a leading neutron in photon - hadron interactions at hadronic colliders

In this paper we study leading neutron production in photon - hadron interactions which take place in $pp$ and $pA$ collisions at large impact parameters. Using a model that describes the recent leading neutron data at HERA, we consider exclusive vector meson production in association with a leading neutron in $pp/pA$ collisions at RHIC and LHC energies. The total cross sections and rapidity distributions of $ρ$, $ϕ$ and $J/Ψ$ produced together with a leading neutron are computed. Our results indicate that the study of these processes is feasible and that it can be used to improve the understanding of leading neutron processes and of exclusive vector meson production.

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arXiv2016

On the rapidity dependence of the average transverse momentum in hadronic collisions

The energy and rapidity dependence of the average transverse momentum $\langle p_T \rangle$ in $pp$ and $pA$ collisions at RHIC and LHC energies are estimated using the Colour Glass Condensate (CGC) formalism. We update previous predictions for the $p_T$ - spectra using the hybrid formalism of the CGC approach and two phenomenological models for the dipole - target scattering amplitude. We demonstrate that these models are able to describe the RHIC and LHC data for the hadron production in $pp$, $dAu$ and $pPb$ collisions at $p_T \le 20$ GeV. Moreover, we present our predictions for $\langle p_T \rangle$ and demonstrate that the ratio $\langle p_{T}(y)\rangle / \langle p_{T}(y = 0)\rangle$ decreases with the rapidity and has a behaviour similar to that predicted by hydrodynamical calculations.

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arXiv2016

Bottom production in Photon and Pomeron -- induced interactions at the LHC

In this paper we present a detailed comparison of the bottom production in gluon -- gluon, photon -- gluon, photon -- photon, pomeron -- gluon, pomeron -- pomeron and pomeron -- photon interactions at the LHC. The transverse momentum, pseudo -- rapidity and $ξ$ dependencies of the cross sections are calculated at LHC energy using the Forward Physics Monte Carlo (FPMC), which allows to obtain realistic predictions for the bottom production with one or two leading intact protons. Moreover, predictions for the the kinematical range probed by the LHCb Collaboration are also presented. Our results indicate that the analysis of the single diffractive events is feasible using the Run I LHCb data.

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arXiv2016

Exclusive processes with a leading neutron in $ep$ collisions

In this paper we extend the color dipole formalism to the study of exclusive processes associated with a leading neutron in $ep$ collisions at high energies. The exclusive $ρ$, $ϕ$ and $J/Ψ$ production, as well as the Deeply Virtual Compton Scattering, are analysed assuming a diffractive interaction between the color dipole and the pion emitted by the incident proton. We compare our predictions with the HERA data on $ρ$ production and estimate the magnitude of the absorption corrections. We show that the color dipole formalism is able to describe the current data. Finally, we present our estimate for the exclusive cross sections which can be studied at HERA and in future electron-proton colliders.

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arXiv2016

Probing the gluon density of the proton in the exclusive photoproduction of vector mesons at the LHC: A phenomenological analysis

The current uncertainty on the gluon density extracted from the global parton analysis is large in the kinematical range of small values of the Bjorken - $x$ variable and low values of the hard scale $Q^2$. An alternative to reduces this uncertainty is the analysis of the exclusive vector meson photoproduction in photon - hadron and hadron - hadron collisions. This process offers a unique opportunity to constrain the gluon density of the proton, since its cross section is proportional to the gluon density squared. In this paper we consider current parametrizations for the gluon distribution and estimate the exclusive vector meson photoproduction cross section at HERA and LHC using the leading logarithmic formalism. We perform a fit of the normalization of the $γh$ cross section and the value of the hard scale for the process and demonstrate that the current LHCb experimental data are better described by models that assume a slow increasing of the gluon distribution at small - $x$ and low $Q^2$.

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arXiv2016

Phenomenological implications of the intrinsic charm in the $Z$ boson production at the LHC

In this paper we study the $Z$, $Z+$ jet, $Z+c$ and $Z+c+$ jet production in $pp$ collisions at the LHC considering different models for an intrinsic charm content of the proton. We analyse the impact of the intrinsic charm in the rapidity and transverse momentum distributions for these different processes. Our results indicated that differently from the other processes, the $Z+c$ cross section is strongly affected by the presence of the intrinsic charm. Moreover, we propose the analysis of the ratios $R(Z+c/Z) \equiv σ(Z+c)/σ(Z)$ and $R(Z+c/Z+\mbox{jet}) \equiv σ(Z+c)/σ(Z+\mbox{jet})$ and demonstrate that these observables can be used as a probe of the intrinsic charm.

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arXiv2015

Double vector meson production in $γγ$ interactions at hadronic colliders

In this paper we revisit the double vector meson production in $γγ$ interactions at heavy ion collisions and present, by the first time, predictions for the $ρρ$ and $J/ΨJ/Ψ$ production in proton -- nucleus and proton -- proton collisions. In order to obtain realistic predictions for rapidity distributions and total cross sections for the double vector production in ultra peripheral hadronic collisions we take into account of the description of $γγ\rightarrow VV$ cross section at low energies as well as its behaviour at large energies, associated to the gluonic interaction between the color dipoles. Our results demonstrate that the double $ρ$ production is dominated by the low energy behaviour of the $γγ\rightarrow VV$ cross section. In contrast, for the double $J/Ψ$ production, the contribution associated to the description of the QCD dynamics at high energies contributes significantly, mainly in $pp$ collisions. Predictions for the RHIC, LHC, FCC and CEPC - SPPC energies are shown.

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arXiv2015

Investigating the effects of the QCD dynamics in the neutrino absorption by the Earth's interior at ultrahigh energies

The opacity of the Earth to incident ultra high energy neutrinos is directly connected with the behaviour of the neutrino - nucleon ($σ^{νN}$) cross sections in a kinematic range utterly unexplored. In this work we investigate how the uncertainties in $σ^{νN}$ due the different QCD dynamic models modify the neutrino absorption while they travel across the Earth. In particular, we compare the predictions of two extreme scenarios for the high energy behaviour of the cross section, which are consistent with the current experimental data. The first scenario considered is based on the solution of the linear DGLAP equations at small-$x$ and large-$Q^2$, while the second one take into account the unitarity effects in the neutrino - nucleon cross section by the imposition of the Froissart bound behaviour in the nucleon structure functions at large energies. Our results indicate that probability of absorption and the angular distribution of neutrino events are sensitive to the the QCD dynamics at ultra high energies.

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