New developments in the statistical approach of parton distributions

We recall how parton distributions are constructed in a statistical physical picture of the nucleon. The chiral properties of QCD lead to strong relations between quarks and antiquarks distributions and the importance of the Pauli exclusion principle is also emphasized. A global next-to-leading order QCD analysis of unpolarized and polarized deep-inelastic scattering data allows to determine a small number of free parameters. Some predictions are compared to recent experimental results and we discuss the prospects of this physical framework.Comment: 10 pages, 12 figures. Invited talk presented at the " Corfu Summer Institute on EPP,CORFU2005, Corfu, Greece, September 4-26, 2005. To be published in Journal of Physics, Conference Series (2006

Determination of two-photon exchange amplitudes from elastic electron-proton scattering data

Using the available cross section and polarization data for elastic electron-proton scattering, we provide an extraction of the two-photon exchange amplitudes at a common value of four-momentum transfer, around Q^2 = 2.5 GeV^2. This analysis also predicts the e^+ p / e^- p elastic scattering cross section ratio, which will be measured by forthcoming experiments.Comment: 4 pages, 5 figures, updated error analysi

Deeply Virtual Compton Scattering off the Neutron

The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e⃗,e′γ)X cross section measured at Q2=1.9  GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to Eq, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced

Investigation of Proton-Proton Short-Range Correlations via the (12)C(e,e′pp) Reaction

We investigated simultaneously the 12C(e,e′p) and 12C(e,e′pp) reactions at Q2=2  (GeV/c)2, xB=1.2, and in an (e, e′p) missing-momentum range from 300 to 600  MeV/c. At these kinematics, with a missing momentum greater than the Fermi momentum of nucleons in a nucleus and far from the delta excitation, short-range nucleon-nucleon correlations are predicted to dominate the reaction. For (9.5±2)% of the 12C(e,e′p) events, a recoiling partner proton was observed back-to-back to the 12C(e,e′p) missing-momentum vector, an experimental signature of correlations

High-Resolution Spectroscopy of Λ(16)N by Electroproduction

An experimental study of the 16O(e,e′K+)Λ16N reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e′K+)Λ,Σ0 exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76±0.16  MeV was obtained for Λ16N with better precision than previous measurements on the mirror hypernucleus Λ16O. Precise energies have been determined for peaks arising from a Λ in s and p orbits coupled to the p1/2 and p3/2 hole states of the 15N core nucleus