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R. J. Hernández-Pinto

Publications and source records attributed to R. J. Hernández-Pinto.

At least 19 recordsLinked to original sources
arXiv2026

Phenomenological extraction of fragmentation functions in a $p\bar{p}$ environment

The precise determination of fragmentation functions (FFs) of hadrons relies on the accurate description of the differential cross sections obtained from both experimental high-energy hadron colliders and theoretical predictions at higher orders in quantum chromodynamics. Various phenomenological strategies have been employed to extract FFs. In this work, we analyze the use of kinematical cuts for reactions including pions and kaons in proton-antiproton collisions to isolate individual FF contributions. This study examines the feasibility of using a similar approach as in proton-proton colliders to analyze FF flavour separation~\cite{Ochoa-Oregon:2023ktx}. In particular, we study photon-hadron production at colliders, including NLO QCD and LO QED corrections to reconstruct the partonic momentum fractions.

hep-ph↗
arXiv2026

Elastic Form Factors of Axial-Vector Mesons: A Contact Interaction Exploration

We employ a symmetry-preserving treatment of the contact interaction within the coupled for- malism of Schwinger-Dyson and Bethe-Salpeter equations to calculate the elastic form factors of axial-vector mesons. In this study, we present the computation of the charge radii, magnetic mo- ments, and quadrupole moments of axial-vector mesons, including those composed of light quarks, heavy quarks or a light and a heavy quark. Our findings indicate that the electric form factor for axial-vector mesons, like that of vector mesons, crosses zero. Furthermore, this crossing occurs at a lower value for axial-vector mesons than for vector mesons. The results for vector-axial mesons follow a similar hierarchy in charge radii as observed for S, PS, and V mesons, with radii decreasing as the mass of the dressed quarks increases. We also include a term associated with the anoma- lous magnetic moment in the quark-photon vertex. This term has a noticeable impact on both the axial-vector magnetic moment and quadrupole moment, leading to significant percentage changes in their values. We compare our results with those obtained from other models whenever available.

hep-ph↗
arXiv2026

A multidimensional landscape of the $η$ and $η'$ mesons

We employ a recently proposed form-invariant algebraic model for the quark propagator and the Bethe-Salpeter amplitude of pseudoscalar mesons to study the internal structure of $η$ and $η'$ mesons. This model facilitates the construction of the Bethe-Salpeter wavefunction, whose projection onto an appropriate flavor-basis leads to the light-front wavefunction for convenient linear combinations of the $s \bar{s}$ and $l\bar{l}\sim(u \bar{u} + d \bar{d})$ states. Using an overlap representation, we compute the valence-quark generalized parton distributions (GPDs). The construction of the model ensures that this multidimensional quantity is determined entirely by the corresponding valence-quark distribution amplitudes. Once the GPDs are constructed, we carry out a straightforward derivation of other desired physical observables such as the distribution functions and the electromagnetic form factors. We also provide explicit comparisons with available results, demonstrating that the present model offers a consistent physical picture for all ground-state pseudoscalar mesons.

hep-ph↗
arXiv2026

Unified analysis of screening masses for vector and axial-vector mesons and their diquark partners in the Contact Interaction model

We present a comprehensive study of the screening masses of vector and axial-vector mesons and their corresponding diquark partners within a symmetry-preserving vector-vector contact interaction approach. Our analysis includes mesons and diquarks composed of both light and heavy quarks, providing a unified description of their thermal behavior. The longitudinal and transverse modes of the screening masses are analyzed, and the results are systematically compared with other theoretical approaches. At $T = 0$ MeV, our predictions agree with available experimental data, and a comparison with the expected free theory limit at high temperatures is also presented. Notably, the parity partners of the lightest mesons and diquarks converge at high temperatures, signaling chiral symmetry restoration within this framework. These results provide a consistent and detailed picture of meson and diquark properties at finite temperature and lay the groundwork for extending the capabilities of the model to baryon screening masses in the quark-diquark picture.

hep-ph↗
arXiv2025

Screening Masses for Scalar and Pseudoscalar Mesons and their Diquark Partners: Insights from the Contact Interaction Model

In this study, we calculate the screening masses of forty spin-zero meson and diquark states composed of light, heavy and heavy-light quarks, within a symmetry-preserving framework based on Dyson-Schwinger equations and a vector $\times$ vector contact interaction. This effective interaction reproduces hadron static properties at $T=0$ MeV that are in close agreement with experimental data and results from more sophisticated interaction kernels. Our analysis reveals that, at temperatures above the critical temperature, the dressed quark masses of the lightest mesons converge toward their respective current quark masses. Our work extends this study up to $T=500$ MeV. Furthermore, we demonstrate that the screening masses of meson parity partners become degenerate above a characteristic temperature, a phenomenon that is likewise reflected in the thermal evolution of their associated Bethe-Salpeter amplitudes (BSAs), providing robust evidence for chiral symmetry restoration. A similar trend is observed for scalar and pseudoscalar diquarks, whose screening masses also converge at high temperatures. As a consequence, these diquarks shall contribute equally to the baryon screening masses in the high-temperature regime. Wherever results from other approaches are available, we perform direct comparisons and observe consistency with our findings.

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

Electric, Magnetic and Quadrupole Form Factors and Charge Radii of Vector Mesons: From Light to Heavy Sector in a Contact Interaction

We present a detailed survey of electric, magnetic and quadrupole form factors of light and heavy spin-1 vector mesons. It complements our analogous analysis of the electromagnetic form factors of pseudoscalar and scalar mesons reported earlier. Our formalism is based upon the Schwinger-Dyson equations treatment of a vector $\times$ vector contact interaction and the Bethe-Salpeter equation description of relativistic two-body bound states. We compute the form factors, associated moments and charge radii, comparing these quantities to earlier theoretical studies and experimental results if and when possible. We also investigate the quark-mass dependence of the charge radii and find the anticipated hierarchy such that it decreases with increasing dressed quark masses. In addition, our analysis shows that the magnetic moment is independent of the mass of the light and heavy mesons. Our results agree with most measurements reported earlier, finding a negative quadrupole moment, implying the charge distribution is oblate.

hep-ph↗
arXiv2024

First Radial Excitations of Baryons in a Contact Interaction: Mass Spectrum

We compute masses of twenty positive parity first radial excitations of spin-$1/2$ and $3/2$ baryons composed of u,d,s,c and b quarks in a quark-diquark picture within a contact interaction model. These excitations comprise of two elements: one characterized by a zero in the Faddeev amplitude, representing a radial excitation of the quark-diquark system and the other marked by a zero in the diquark's Bethe-Salpeter amplitude, corresponding to an intrinsic excitation of the diquark correlation. Wherever possible, we compare our results with other models and/or experiment. We verify that the masses obtained through our model conform to the spacing rules for all the baryons studied, whether light or heavy and whether of spin 1/2 or 3/2. The computed masses do not just offer a guide to the future experimental searches but also compare well with the existing candidates for the possible radial excitations of some heavy baryons.

hep-ph↗
arXiv2024

Electromagnetic and two-photon transition form factors of the pseudoscalar mesons: An algebraic model computation

We compute electromagnetic and two-photon transition form factors of ground-state pseudoscalar mesons: $π,\,K,\,η_c,\,η_b$. To this end, we employ an algebraic model based upon the coupled formalism of Schwinger-Dyson and Bethe-Salpeter equations. Within this approach, the dressed quark propagator and the relevant Bethe-Salpeter amplitude encode the internal structure of the corresponding meson. Electromagnetic properties of the meson are probed via the quark-photon interaction. The algebraic model employed by us unifies the treatment of all ground-state pseudoscalar mesons. Its parameters are carefully fitted performing a global analysis of existing experimental data including the knowledge of the charge radii of the mesons studied. We then compute and predict electromagnetic and two-photon transition form factors for a wide range of probing photon momentum-squared which is of direct relevance to the experimental observations carried out thus far or planned at different hadron physics facilities such as the Thomas Jefferson National Accelerator Facility (JLab) and the forthcoming Electron-Ion Collider. We also present comparisons with other theoretical models and approaches and lattice quantum chromodynamics.

hep-ph↗
arXiv2023

Artificial Intelligence for the Electron Ion Collider (AI4EIC)

The Electron-Ion Collider (EIC), a state-of-the-art facility for studying the strong force, is expected to begin commissioning its first experiments in 2028. This is an opportune time for artificial intelligence (AI) to be included from the start at this facility and in all phases that lead up to the experiments. The second annual workshop organized by the AI4EIC working group, which recently took place, centered on exploring all current and prospective application areas of AI for the EIC. This workshop is not only beneficial for the EIC, but also provides valuable insights for the newly established ePIC collaboration at EIC. This paper summarizes the different activities and R&D projects covered across the sessions of the workshop and provides an overview of the goals, approaches and strategies regarding AI/ML in the EIC community, as well as cutting-edge techniques currently studied in other experiments.

physics.acc-ph↗
arXiv2023

Electromagnetic Form Factors and Charge Radii of Pseudoscalar and Scalar Mesons: A Comprehensive Contact Interaction Analysis

We carry out a comprehensive survey of electromagnetic form factors of all light, heavy and heavy-light ground-state pseudoscalar and scalar mesons. Our analysis is based upon a Schwinger-Dyson equations treatment of a vector $\times$ vector contact interaction. It incorporates confinement and ensures axial vector and vector Ward-Takahashi identities are satisfied along with the corresponding corollaries such as the Goldberger-Treiman relations. The algebraic simplicity of the model allows us to compute the form factors at arbitrarily large virtualities of the probing photon momentum squared with relative ease. Wherever possible and insightful, we compare our results for the electromagnetic form factors and the charge radii with those obtained earlier through Schwinger-Dyson equations, lattice and with experimental observations available. We also comment on the scope and shortcomings of the model.

hep-ph↗
arXiv2022

Elastic meson form factors in a unified scheme

The extraction of elastic form factors for mesons in the context of the contact interaction model is revisited in this manuscript. The dressed masses of quarks and mesons are determined through the gap and Bethe-Salpeter equations. The generic elastic scattering process $Mγ\to M$ is studied for the meson $M$ formed of two differently flavored quarks. The charge radii of scalar, pseudoscalar, vector and axial-vector mesons are also extracted by virtue of explicit calculation of the meson elastic form factors.

hep-ph↗
arXiv2019

Spherocity study for e^{+}e^{-} Fragmentation Functions using Pythia MC generator

The Fragmentation Functions is one of the non-perturbative components of the QCD factorization theorem. They represents the probability of a parton carrying a fraction z of momentum to form into a particular kind of hadron. In this work, we study the jet fragmentation functions in the collisions between electrons and positrons. The jets where identified with Fastjet for different p_{Tch jet} intervals. The intervals and the final jets were reconstructed by means of the event shape T separation using spherocity variable, the study is performed under Pythia Monte Carlo event generator framework.

hep-ph↗
arXiv2017

Global extraction of the parton-to-kaon fragmentation functions at NLO in QCD

In this document, we present the global QCD analysis of parton-to-kaon fragmentation functions at next-to-leading order accuracy using the latest experimental information on single-inclusive kaon production in electron-positron annihilation, lepton-nucleon deep-inelastic scattering, and proton-proton collisions. An extended analysis of this work can be found in Ref.[1].

hep-ph↗
arXiv2016

NLO cross sections in 4 dimensions without DREG

In this review, we present a new method for computing physical cross sections at NLO accuracy in QCD without using the standard Dimensional Regularisation. The algorithm is based on the Loop-Tree Duality theorem, which allow us to obtain loop integrals as a sum of phase-space integrals; in this way, transforming loop integrals into phase-space integrals, we propose a method to merge virtual and real contributions in order to find observables at NLO in $d=4$ space-time dimensions. In addition, the strategy described is used for computing the $γ^*\to q\bar{q}(g)$ process. A more detailed discussion related on this topic can be found in Ref [1].

hep-ph↗
arXiv2014

QCD Phenomenology

Quantum Chromodynamics is the most successful theory in particle physics. The understanding of all different signals at hadron colliders have been achieved due to the correct interpretation of the theory. In this paper we review some basic features of the theory of strong interactions and how it could be used in order to provide phenomenological distributions for the Large Hadron Collider. The main results presented in here can be found in Ref [1].

hep-ph↗
arXiv2013

A complete O(alpha_S^2) calculation of the signal-background interference for the Higgs diphoton decay channel

We present the full ${\cal O}(\as^2)$ computation of the interference effects between the Higgs diphoton signal and the continuum background at the LHC. While the main contribution to the interference originates on the $gg$ partonic subprocess, we find that the corrections from the $qg$ and $q\bar{q}$ channels amount up to 35% of it. We discuss the effect of these new subprocesses in the shift of the diphoton invariant mass peak recently reported by S. Martin in Ref.\cite{Martin:2012xc}.

hep-ph↗