Extraction of Compton Form Factors from DVCS data

We present the results of a fitter code which aims at extracting Compton Form Factors (CFFs) from DVCS (Deep Virtual Compton Scattering) experimental data, in a largely model-independent way. CFFs are linked to GPDs (Generalized parton Distributions) and are the quantities which are directly measurable. The data that we have analyzed are from JLab and HERMES experiments. We obtain some first important constraints on the $H$ and $\tilde{H}$ CFFs. The kinematical dependences ($x_B$, $t$) of these CFFs provide some new insights on nucleon structure.Comment: 5 pages, 1 figure. Proceeding of ICHEP10 conference, July 22-28, 201

Generalized Parton Distributions : Experimental aspects

After briefly outlining the formalism of the Generalized Parton Distributions (GPDs) in the first sections, we discuss some general considerations for their experimental study : in particular, the relation between GPDs and experimental observables and the need and requirements for a dedicated experimental facility. Also, we review and comment the first experimental signatures of this physics recently observed by the HERMES and CLAS (at JLab) collaborations.Comment: 10 pages, Invited talk at ICTP 3rd International Conference on Perspectives in Hadronic Physics, Trieste, Italy, 7-11 May 2001. Submitted to Nucl.Phys.

Deeply pseudoscalar meson electroproduction with CLAS and Generalized Parton Distributions

We discuss the recent data of exclusive $\pi^0$ (and $\pi^+$) electroproduction on the proton obtained by the CLAS collaboration at Jefferson Lab. It is observed that the cross sections, which have been decomposed in $\sigma_T +\epsilon\sigma_L$, $\sigma_{TT}$ and $\sigma_{LT}$ structure functions, are dominated by transverse amplitude contributions. The data can be interpreted in the Generalized Parton Distribution formalism provided that one includes helicity-flip transversity GPDs.Comment: 4 pages, 2 figures PANIC14 conference proceedin

Deeply Virtual Electroproduction of Photons and Mesons

In this paper, after a brief summary of the properties of the Off-Forward Parton Distributions, we give some examples of what could be the experimental opportunities to access them at the current high-energy lepton facilities : JLab (E_e >= 6 GeV), HERMES (E_e = 27 GeV) and COMPASS (E_mu = 200 GeV).Comment: 5 pages, 3 figure

Analysis of Deeply Virtual Compton Scattering Data at Jefferson Lab and Proton Tomography

The CLAS and Hall A collaborations at Jefferson Laboratory have recently released new results for the ep->ep{\gamma} reaction. We analyze these new data within the Generalized Parton Distribution formalism. Employing a fitter algorithm introduced and used in earlier works, we are able to extract from these data new constraints on the kinematical dependence of three Compton Form Factors. Based on experimental data, we subsequently extract the dependence of the proton charge radius on the quarks longitudinal momentum fraction.Comment: 25 pages, 26 figure

Role of nucleon resonance excitation in ϕ\phi meson photoproduction

The resonance effects are investigated in the $\phi$ meson photoproduction near threshold through a quark model approach with an effective Lagrangian. The diffractive contribution is consistently estimated by the {\it t}-channel Pomeron exchange. Another non-diffractive process, {\it t}-channel $\pi^0$ exchange is also included. The numerical result shows that the Pomeron exchange plays dominant role in the $\phi$ meson photoproduction, while the cross sections of the non-diffractive processes, i.e. {\it s}- and {\it u}-channel excitations, and {\it t}-channel $\pi^0$ exchange, are quite small. In the polarization observables, we find that large asymmetries are produced in the backward direction by the interferences from the {\it s}- and {\it u}-channel resonances, while in the forward direction, only very small asymmetries are generated. Meanwhile, we find that the effects from the $\pi^0$ exchange are generally negligible.Comment: Contribution to "2nd International Conference on Perspectives in Hadronic Physics", Trieste, ICTP, 10-14 May 1999, to appear in Few-body Syste

Timelike Compton Scattering off the Proton: beam and/or target spin asymmetries

We present a sample of results of our work to be published soon on Timelike Compton scattering off the proton, in the framework of the Generalized Parton Distributions formalism.Comment: 2 figures, 4 pages, PANIC 2014 conference proceedin