No abstract

International audienceThe Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous ElectronBeam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization fromelectrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electronbeam in a high-Z target. Positron polarization up to 82% have been measured for an initial electron beammomentum of 8.19 MeV=c, limited only by the electron beam polarization. This technique extendspolarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positronbeam physics to a wide community

The internal structure of nucleons (protons and neutrons) remains one of the greatest outstanding problems in modern nuclear physics. By scattering high-energy electrons off a proton we are able to resolve its fundamental constituents and probe their momenta and positions. Here we investigate the dynamics of quarks and gluons inside nucleons using deeply virtual Compton scattering (DVCS)—a highly virtual photon scatters off the proton, which subsequently radiates a photon. DVCS interferes with the Bethe-Heitler (BH) process, where the photon is emitted by the electron rather than the proton. We report herein the full determination of the BH-DVCS interference by exploiting the distinct energy dependences of the DVCS and BH amplitudes. In the regime where the scattering is expected to occur off a single quark, measurements show an intriguing sensitivity to gluons, the carriers of the strong interaction.

No abstract

Double-spin asymmetries and absolute cross sections were measured at large Bjorken x ð0.25 ≤ x ≤ 0.90Þ, in both the deep-inelastic and resonance regions, by scattering longitudinally polarized electrons at beam energies of 4.7 and 5.9 GeV from a transversely and longitudinally polarized 3 He target. In this dedicated experiment, the spin structure function g 3 He 2 was determined with precision at large x, and the neutron twist-3 matrix element d n 2 was measured at hQ 2 i of 3.21 and 4.32 GeV 2 =c 2 , with an absolute

We report the first measurement of the target single-spin asymmetry, A y , in quasielastic scattering from the inclusive reaction 3 He ↑ ðe; e 0 Þ on a 3 He gas target polarized normal to the lepton scattering plane.