arXiv subjects

V. P. Gonçalves

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

16 recordsLinked to original sources

arXiv2025

Brazilian Report on Dark Matter 2024

One of the key scientific objectives for the next decade is to uncover the nature of dark matter (DM). We should continue prioritizing targets such as weakly-interacting massive particles (WIMPs), Axions, and other low-mass dark matter candidates to improve our chances of achieving it. A varied and ongoing portfolio of experiments spanning different scales and detection methods is essential to maximize our chances of discovering its composition. This report paper provides an updated overview of the Brazilian community's activities in dark matter and dark sector physics over the past years with a view for the future. It underscores the ongoing need for financial support for Brazilian groups actively engaged in experimental research to sustain the Brazilian involvement in the global search for dark matter particles

hep-ph↗

arXiv2025

The glue that binds us all -- Latin America and the Electron-Ion Collider

The Electron-Ion Collider, a next generation electron-hadron and electron-nuclei scattering facility, will be built at Brookhaven National Laboratory. The wealth of new data will shape research in hadron physics, from nonperturbative QCD techniques to perturbative QCD improvements and global QCD analyses, for the decades to come. With the present proposal, Latin America based physicists, whose expertise lies on the theory and phenomenology side, make the case for the past and future efforts of a growing community, working hand-in-hand towards developing theoretical tools and predictions to analyze, interpret and optimize the results that will be obtained at the EIC, unveiling the role of the glue that binds us all. This effort is along the lines of various initiatives taken in the U.S., and supported by colleagues worldwide, such as the ones by the EIC User Group which were highlighted during the Snowmass Process and the Particle Physics Project Prioritization Panel (P5).

nucl-ex↗

arXiv2024

Investigating the Timelike Compton scattering in photon-proton interactions at the EIC

Information about the 3-dimensional description of the quark and gluon content of hadrons, described by the generalized parton distributions (GPDs), can be probed by exclusive processes in electron - proton ($ep$) collisions. In this letter, we investigate the timelike Compton scattering (TCS) in $ep$ collisions at the future electron - ion collider (EIC). Such process is characterized by the exclusive dilepton production through the subprocess $γp \rightarrow γ^*p \rightarrow l^+ l^- p$, with the real photon in the initial state being emitted by the incoming electron. Assuming a given model for the GPDs, the TCS differential cross-section is estimated, as well the contribution associated to the interference between the TCS and Bethe - Heitler (BH) amplitudes. Predictions for the TCS, BH and interference contributions are presented considering the kinematical range expected to be covered by the EIC detectors. Moreover, the polarized photon asymmetry is also studied. Our results indicated that a future experimental analysis, considering photon circular polarizations, can be useful to probe the interference contribution and constrain the description of the GPDs for the proton.

hep-ph↗

arXiv2023

Searching for a Leptophilic Z' and a 3-3-1 symmetry at CLIC

We derive the discovery potential of a leptophilic Z', and a Z' rising from a $SU(3) \times SU(3)_L \times U(1)_N$ symmetry at the Compact Linear Collider (CLIC), which is planned to host $e^+e^-$ collisions with 3 TeV center-of-mass energy. We perform an optimized selection cut strategy on the transverse momentum, pseudorapidity, and invariant mass of the dileptons in order to enhance the collider sensitivity. We find that CLIC can potentially reach a $5σ$ signal of a $1-3$~TeV leptophilic Z' with less than $1fb^{-1}$ of integrated luminosity. As for the Z' belonging to a 3-3-1 symmetry, CLIC will offer a complementary probe with the potential to impose $M_{Z^\prime} > 3$~TeV with $\mathcal{L}=2fb^{-1}$.

hep-ph↗

arXiv2023

Leading $Λ$ production in future electron-proton colliders

Leading $Λ$ (LL) production in $ep$ collisions at high energies is investigated using the color dipole formalism and taking into account the nonlinear QCD effects. In particular, the impact of the absorptive effects on the LL spectra are estimated considering the kinematical range that will be probed by the Electron Ion Collider (EIC) and by the Large Hadron electron Collider (LHeC). Our results indicate that the LL spectrum is strongly suppressed at small photon virtualities. These results suggest that absorptive effects are not negligible and should be taken into account in order to extract the kaon structure function from data on leading $Λ$ production.

hep-ph↗

arXiv2020

Leading neutron production at the EIC and LHeC: estimating the impact of the absorptive corrections

Leading neutron (LN) production in $ep$ collisions at high energies is investigated using the color dipole formalism and taking into account saturation effects. We update the treatment of absorptive effects and estimate the impact of these effects on LN spectra in the kinematical range that will be probed by the Electron Ion Collider (EIC) and by the Large Hadron electron Collider (LHeC). We demonstrate that Feynman scaling, associated to saturation, is not violated by the inclusion of absorptive effects. Moreover, our results indicate that the LN spectrum is strongly suppressed at small photon virtualities. These results suggest that absorptive effects cannot be disregarded in future measurements of the $γπ$ cross section to be extracted from data on leading neutron production.

hep-ph↗

arXiv2015

Tetraquark Production in Double Parton Scattering

We develop a model to study tetraquark production in hadronic collisions. We focus on double parton scattering and formulate a version of the color evaporation model for the production of the $X(3872)$ and of the $T_{4c}$ tetraquark, a state composed by the $c \bar{c} c \bar{c}$ quarks. We find that the production cross section grows rapidly with the collision energy $\sqrt{s}$ and make predictions for the forthcoming higher energy data of the LHC.

hep-ph↗

arXiv2015

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.

hep-ph↗

arXiv2013

Charm production in double parton scattering at the LHC

We calculate $c\bar{c}c\bar{c}$ and $b\bar{b}b\bar{b}$ production cross section in Double Parton Scattering (DPS) processes at the energies of LHC. In our calculation we include saturation effects in the gluon distribution. For charm production, our results confirm the prediction of a previous work in which saturation effects were neglected, namely that at the energies of LHC charm production in DPS processes becomes comparable with charm production in SPS. We also estimate the production of $c\bar{c}b\bar{b}$ in DPS. Our results indicate that at $\sqrt{s}=14$ TeV half of the total amount of bottom produced in proton-proton collisions comes from this process.

hep-ph↗

arXiv2008

Could saturation effects be visible in a future electron-ion collider?

We expect to observe parton saturation in a future electron - ion collider. In this letter we discuss this expectation in more detail considering two different models which are in good agreement with the existing experimental data on nuclear structure functions. In particular, we study the predictions of saturation effects in electron - ion collisions at high energies, using a generalization for nuclear targets of the b-CGC model, which describes the $ep$ HERA quite well. We estimate the total, longitudinal and charm structure functions in the dipole picture and compare them with the predictions obtained using collinear factorization and modern sets of nuclear parton distributions. Our results show that inclusive observables are not very useful in the search for saturation effects. In the small $x$ region they are very difficult to disentangle from the predictions of the collinear approaches . This happens mainly because of the large uncertainties in the latter. On the other hand, our results indicate that the contribution of diffractive processes to the total cross section is about 20 % at large A and small Q^2, allowing for a detailed study of diffractive observables. The study of diffractive processes becomes essential to observe parton saturation.

hep-ph↗

arXiv2001

The Diffractive Logarithmic Slope and the Saturation Phenomena

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.

hep-ph↗

arXiv2000

The Asymptotic Regime of High Density QCD

We discuss the distinct approaches for high density QCD (hdQCD) in the asymptotic regime of large values of parton density. We derive the AGL equation for running coupling constant and obtain the asymptotic solution, demonstrating that the property of partial saturation of the solution of the AGL equation is not modified by the running of the coupling constant. We show that in this kinematical regime, the solution of the AGL equation coincides with the solution of an evolution equation, obtained recently using the McLerran-Venugopalan approach. Using the asymptotic behavior of the gluon distribution we calculate the $F_2$ structure function assuming first that the leading twist relation between these two quantities is valid and second that this relation is modified by the higher twist terms associated to the unitarity corrections. In the first case we obtain that the corresponding $F_2$ structure function is linearly proportional to $ln s$, which agrees with the results obtained recently by Kovchegov using a distinct approach. In the second case a softer behavior is obtained. In both cases, the $F_2$ structure function unitarizes and the Froissart boundary is not violated in the asymptotic regime of high density QCD. We conclude that the partial saturation of the gluon distribution and the unitarization of the structure function are general results, well-established by three distinct approaches for high dense systems.

hep-ph↗

arXiv1999

The High Density Parton Dynamics from Eikonal and Dipole Pictures

In this contribution we discuss distinct approaches for the high density QCD (hdQCD) and the demonstration of the equivalence between the AGL approach and the K approach is presented. Our conclusion is that the AGL equation is a good candidate for an unitarized evolution equation at high densities in the DLA limit.

hep-ph↗

arXiv1999

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.

hep-ph↗

arXiv1999

Seeking the Shadowing in eA Processes

We consider the behavior of the slope of the nuclear structure function $F_2^A$ in the kinematic region which will be explored in the eA HERA collider. We demonstrate that, similarly to the nucleon case, a `turn over' is predicted in this observable. Moreover, we predict that the presence of the shadowing corrections implies that the maximum value of the slope is dependent of the number of nucleons A, differently from the DGLAP predictions. Our conclusion is that the measurement of this observable will allow to evidentiate the presence of the shadowing corrections.

hep-ph↗

arXiv1999

The AGL Equation from a 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 contribution that the AGL equation can also be obtained from the dipole picture. Our conclusion is that the AGL equation is a good candidate for an unitarized evolution equation at small $x$ in the DLA limit.

hep-ph↗