In this manuscript, we present the results of our studies on the exclusive photoproduction of quarkonium-photon pairs with large invariant mass. In our analysis, we focus on the production of the ηcγ and χcJγ pairs in high energy kinematics. We use the Color Glass Condensate (CGC) framework for analysis and demonstrate that at leading order in αs the cross-sections of these processes are determined by the forward dipole scattering amplitude. The kinematic distributions of the produced particles allow us to study the dipole amplitude in detail, making this process a very clean probe for studies of saturation physics. Using phenomenological parametrizations of the dipole amplitudes, we estimate numerically the differential production cross-sections for ηcγ and χcγ in the kinematics of ultraperipheral collisions at the LHC and the future Electron-Ion Collider (EIC). Furthermore, we assess the role of this process as a possible background to the exclusive photoproduction of C-even quarkonia, which is frequently considered as a tool for odderon searches.
We study the process of double parton scattering (DPS) associated with the photoproduction at a future Electron-Ion collider (EIC) and HERA. We show that in the case of the resolved photon the 1 to 2 processes lead, even at small transverse momenta of the hard processes , to the increase of the DPS by a factor of order 1.6 in the significant part of the phase space, relative to the predictions of the mean field based models . Moreover we study the kinematic region where direct photon contribution is dominant and show it s boundaries for charm and light quark jets. For charmed jets we see that the relevant region is $x_\gamma\ge 0.2-0.4$. This region is even enhanced if we consider the photoproduction on the nuclei.
We study exclusive electroproduction of heavy quark-antiquark pairs off nucleons in the framework of generalized transverse momentum dependent parton distributions (GTMDs) for gluons. The short-distance part of the process is treated at leading order in perturbative Quantum Chromodynamics and in first order in a collinear expansion, which allows identification with the description in terms of Generalized Parton Distributions (GPDs). For the results for the structure functions in terms of GTMDs and GPDs we consider only unpolarized (spin-averaged) nucleons, but include all possible azimuthal modulations that can arise. The presented results extend known expressions in the literature and are relevant for experimental studies of this exclusive process at the future Electron Ion Collider. Furthermore, we introduce a convenient decomposition of the gluon-gluon correlation matrix in terms of GTMDs, expanded in a Lorentz basis of symmetric traceless tensors obtained from the partonic momentum $k_T$ and the momentum transfer $\Delta_T$. The adopted notation for the GTMDs relates to the nucleon helicity states at the amplitude level, rather than to polarization states of the incoming nucleon or of the gluons, which makes it more transparent which contributions from helicity difference and helicity flip matrix elements can be accessed with unpolarized nucleon beams.
Mattia Bellotti, Daniël Boer, C. Pisano· 0 citations
In this manuscript, we analyze the contribution of fragmentation mechanisms to the inclusive hadroproduction of heavy quarkonium pairs, taking into account both single- and double-hadron (dihadron) fragmentation channels. To estimate the contribution of the latter mechanism, we construct a microscopic perturbative model of the dihadron fragmentation function, which is valid in the limit of large invariant masses of the heavy quarkonium pair. Using the Color Glass Condensate framework to evaluate the $Q\bar{Q}$ production amplitude, we find that in LHC kinematics, the single fragmentation of heavy quarks into quarkonium is only a minor correction, whereas dihadron fragmentation can provide a sizable contribution, on par with the contributions of single- and double-parton scattering.
This paper studies the production of D∗-mesons in deep inelastic scattering of electrons on protons within the framework of the leading approximation in the strong coupling constant in the collinear parton model and in the parton Reggeization approach. The hadronization of c-quarks is described within the Peterson fragmentation model taking into account the masses of c-quarks and D∗-mesons. The calculations were performed using the KaTie parton level generator and unintegrated parton distribution functions in the modified Kimber – Martin – Ryskin – Watt model. It is shown that the experimental data of the ZEUS and H1 collaborations, obtained at energies √s = 300 − −319 GeV, are in satisfactory agreement with theoretical calculations, with the exception of the region of high D∗-meson pseudorapidity. No significant differences are observed in the predictions of the collinear parton model and the parton Reggeization approach. Predictions are made for various differential cross sections for the production of D∗-mesons at the EIC collider energy, √s = 140 GeV.
V. Saleev, F. M. Shapurin· Vestnik of Samara University...· 0 citations
All-heavy pentaquarks provide a unique laboratory for exploring the interplay between exotic-hadron structure, heavy-quark dynamics, and perturbative Quantum Chromodynamics (QCD). In this review, we present the completed release of the uncertainty-aware collinear fragmentation-function family PQ5Q1.1, covering both all-charm (P5c) and all-bottom (P5b) states. The extension to the bottom sector follows the resolution of theoretical and numerical issues affecting heavy-bottom fragmentation and completes the public LHAPDF6 release of the PQ5Q1.1 family. The PQ5Q1.1 functions are constructed within a multimodal framework that accounts for both compact multiquark formation and diquark–antiquark–diquark production mechanisms. A replica-based strategy is adopted to quantify perturbative and nonperturbative uncertainties through missing-higher-order variations (F-MHOUs) and controlled modifications of the hadronic wave-function structure (F-NPWF). For phenomenological applications, we employ the data-validated (sym)JETHAD framework to investigate semi-inclusive pentaquark-plus-jet production at NLL/NLO+ accuracy at the High-Luminosity Large Hadron Collider. We present predictions for differential distributions, assessing the impact of fragmentation dynamics, uncertainty propagation, and hadron-structure effects across the charm and bottom sectors. By combining precision fragmentation tools with collider-oriented observables, this review establishes a unified framework connecting heavy-pentaquark spectroscopy, hadronization mechanisms, and high-energy QCD phenomenology.
Heavy-flavor jets and their substructure provide a unique window into the role of quark mass on QCD radiation and its modification in nuclear matter. In this work, we investigate heavy-quark energy-energy correlators (EECs) that are explicitly sensitive to mass effects, focusing on angular distributions, energy flow, and the dead-cone effect. We demonstrate how the finite mass of charm and bottom quarks reshapes the intra-jet radiation pattern, leading to characteristic suppression at small angles and measurable deviations from massless jet expectations. Using effective field theory analysis, we extend the calculation of these observables to reactions with nuclei to show that medium-induced radiation competes with vacuum mass suppression, resulting in a nontrivial modification of jet substructure. Specifically, we identify regimes where EECs are dominated by the heavy quark mass, leading to qualitatively and quantitatively different behavior of this observable in QCD matter. We discuss the charm and bottom jet energy-energy correlators modification in reactions with nuclei, and further demonstrate how the formalism can be tested in small collision system at current facilities.