arXiv subjects
Publications and source records attributed to L. Szymanowski.
Exclusive processes of heavy meson production and spacelike and timelike deeply virtual Compton scattering allow us to investigate the hadron structure in terms of Generalized Parton Distributions (GPDs). We review recent developments in the NLO description of such processes.
We study the impact factor for the photon to quark, antiquark and gluon transition within Balitsky's shock-wave formalism. Our aim is to extend existing results beyond approximations discussed in the literature. We present our results of the real contribution, and present some intermediate results on virtual contributions for the photon to quark, antiquark transition.
We report on our NLL BFKL studies of Mueller-Navelet jets. We first perform a complete NLL BFKL analysis supplemented by a BLM renormalization scale fixing procedure, which is successfully compared with recent CMS data. Second, we argue for the need of a measurement of an asymmetric jet configuration in order to perform a valuable comparison with fixed order approaches. Third, we predict that the energy-momentum violation is rather tiny in the NLL BFKL approach, for an asymmetric jet configuration. Finally, we argue that the double parton scattering contribution is negligible in the kinematics of actual CMS measurements.
Photoproduction of a pair of particles with large invariant mass is a natural extension of collinear QCD factorization theorems which have been much studied for deeply virtual Compton scattering and deeply virtual meson production. We consider the case where the wide angle Compton scattering subprocess $γ(q\bar q) \to γρ$ factorizes from generalized parton distribution. At dominant twist, separating the transverse (respectively longitudinal) polarization of the $ρ$ meson allows one to get access to chiral-odd (respectively chiral-even) GPDs. This opens a new way to the extraction of these elusive transversity GPDs.
In view of future phenomenological applications, we study the impact factor for the photon to quark, antiquark and gluon transition within Balitsky's shock-wave formalism. The aim of the present program is to extend existing results beyond approximations discussed in the literature. We present our results of the real contribution, and report on recent progress in calculating the virtual contributions for the photon to quark, antiquark transition.
We study the production of a forward $J/ψ$ meson and a backward jet with a large rapidity separation at the LHC using the BFKL formalism. We compare the predictions given by the Non Relativistic QCD (NRQCD) approach to charmonium prediction and by the Color Evaporation Model. In NRQCD, we find that the $^3 S_1^{\, 8}$ part of the onium wavefunction is completely dominating the process. NRQCD and the color evaporation model give similar results, although a discrepancy seems to appear as the value of the transverse momenta of the charmonium and of the jet decrease.
Generalized parton distributions (GPDs) enter QCD factorization theorems for hard exclusive reactions. They encode rich information about hadron partonic structure. We explore a possibility to constrain GPDs in experiments at LHC considering two different exclusive processes: the timelike Compton scattering and the photoproduction of heavy vector mesons.
We propose a model to study the importance of double parton scattering (DPS) in Mueller-Navelet jets production at the LHC which is consistent with the BFKL framework used to compute the single parton scattering contribution to this process. We study this model in kinematics corresponding to existing and possible future measurements at the LHC and estimate the importance of this DPS contribution on relevant observables for this process, namely the cross section and the azimuthal correlation of the jets.
We demonstrate that the transversity chiral odd generalized parton distributions can be accessed through the azimuthal dependence of the nu N -> l D N' or nubar N -> l D N' differential cross sections, in the framework of the colinear QCD approach, where GPDs factorize from perturbatively calculable coefficient functions calculated up to order mc/Q.
We calculate the amplitude for exclusive neutrino production of a charmed meson on an unpolarized target, in the colinear QCD approach where generalized parton distributions (GPDs) factorize from perturbatively calculable coefficient functions. We demonstrate that the transversity chiral odd GPDs contribute to the transverse cross section if the hard amplitude is calculated up to order mc/Q. We show how to access these GPDs through the azimuthal dependence of the nu N -> mu D N differential cross section.
We provide a concise overview on transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum q_T spectra of Higgs and vector bosons for low q_T, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present an application of a new tool, TMDlib, to parton density fits and parameterizations.
The process of exclusive heavy vector meson photoproduction, gamma p -> V p, is studied in the framework of QCD factorization. The mass of the produced meson, V = Upsilon or J/Psi, provides a hard scale for the process. We demonstrate, that in the heavy quark limit and at the one-loop order in perturbation theory, the amplitude factorizes in a convolution of a perturbatively calculable hard-scattering amplitude with the generalized parton densities and the nonrelativistic QCD matrix element _V. We evaluate the hard scattering amplitude at one-loop order and compare the data with theoretical predictions using an available model for generalized parton distributions.
The process of a light neutral vector meson electroproduction is studied in the framework of QCD factorization in which the amplitude factorizes in a convolution of the nonperturbative meson distribution amplitude and the generalized parton densities with the perturbatively calculable hard-scattering amplitudes. We derive a complete set of hard-scattering amplitudes at next-to-leading order for the production of vector mesons, $V=ρ^0, ω, ϕ$.
We investigate the potentialities offered by the study of lepton-pair production in ultraperipheral collisions at a fixed-target experiment using the proton and ion LHC beams. In these collisions, exclusive or semi-exclusive lepton-pair production can be used as luminosity monitor as well as a check of the equivalent-photon approximation, via the measurement of the Bethe-Heitler cross section. It can also serve as a probe of the inner hadron structure via the measurement of the lepton-pair azimuthal asymmetry which is sensitive to the timelike virtual Compton scattering. We also briefly discuss the possibility offered by the study of eta(c) production. Finally, we outline the possibilities for lepton-pair production by Pomeron-Odderon fusion in exclusive pp and pA collisions.
We consider backward vector meson exclusive electroproduction off nucleons in the framework of collinear QCD factorization. Nucleon to vector meson transition distribution amplitudes arise as building blocks for the corresponding factorized amplitudes. In the near-backward kinematics, the suggested factorization mechanism results in the dominance of the transverse cross section of vector meson production ($σ_T \gg σ_L$) and in the characteristic $1/Q^8$-scaling behavior of the cross section. We evaluate nucleon to vector meson TDAs in the cross-channel nucleon exchange model and present estimates of the differential cross section for backward $ρ^0$, $ω$ and $ϕ$ meson production off protons. The resulting cross sections are shown to be measurable in the forthcoming JLab@12 GeV experiments.
We summarize recent developments in the study of high-energy resummation effects in Mueller-Navelet jets production at the LHC and discuss possible relations with multiparton interactions.
We present the calculation of the impact factor for the photon to quark, antiquark and gluon transition within Balitsky's shock-wave formalism. We also rederive the impact factor for photon to quark and antiquark transition. These results provide the necessary building blocks for further phenomenological studies of inclusive diffractive deep inelastic scattering as well as for two and three jets diffractive production which go beyond approximations discussed in the literature.
Ultraperipheral collisions in hadron colliders give new opportunites to investigate the hadron stucture through exclusive photoproduction processes. We describe the possibility of measuring the Generalized Parton Distributions in the Timelike Compton Scattering process and in the production of heavy vector meson.