[en] Experiment E02-013¹ at Thomas Jefferson National Accelerator Facility (Jefferson Lab) will measure the neutron electric form factor GnE at the high four-momentum transfer values of Q² ∼ 1.3, 2.4 and 3.4 (GeV/c)2 via a measurement of the cross section asymmetry A T in the reaction 3He(e,e'n)pp. This measurement was approved for 32 days of running by Jefferson Lab PAC 21² in January 2002

[en] There is an active program of few-body form factor measurements in Hall A of Thomas Jefferson National Accelerator Facility (Jefferson Laboratory). Recent measurements of the deuteron elastic electric, A(Q2), and magnetic, B(Q2), structure functions will be presented. Planned measurements of the form factors of 3He and 4He will also be discussed

[en] Two recent experiments in Hall A of Jefferson Lab have explored the spin structure of the neutron. Experiment E99-117 focused on measuring the neutron spin asymmetry A₁ⁿ to high precision at x = 0.33, 0.47 and 0.60 and Q² = 2.7, 3.5 and 4.8 (GeV/c)², respectively. A second experiment, E97-103, measured the polarized spin structure function g₂ⁿ at x ∼ 0.2 for five values of the momentum transfer Q² from 0.58 to 1.36 (GeV/c)². Preliminary results from these experiments will be presented and compared to theoretical models

[en] The cross section for elastic electron-deuteron scattering was measured in Jefferson Lab experiment 91-026. The deuteron elastic structure functions A(Q²) and B(Q²) have been extracted from the data. The final results for the electric structure function, A(Q²), in the range of 0.7< or=Q²< or=6.0 (GeV/c)², are presented. Preliminary results for the magnetic structure function, B(Q²), are presented in the range of 0.7< or=Q²< or=1.35 (GeV/c)2. These data are compared to the theoretical predictions of both meson-nucleon and quark-gluon based models

[en] We present measurements of the recoil proton polarization for the ¹H(gamma-vector,p-vector)pi⁰ reaction for theta_c.m.^pi = 60^o-135^o and for photon energies up to 4.1 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. Various theoretical models are compared with the results. No evidence for hadron helicity conservation is observed. Models that employ factorization are not favored. It appears from the strong angular dependence of the induced polarization at photon energies of 2.5 and 3.1 GeV that a relatively high spin resonance or background amplitude might exist in this energy region

[en] We have measured the nuclear transparency of the fundamental process γ n → π^- p in ⁴He. These measurements were performed at Jefferson Lab in the photon energy range of 1.6 to 4.5 GeV and at θ_cm^π = 70^o and 90^o. These measurements are the first of their kind in the study of nuclear transparency in photoreactions. They also provide a benchmark test of Glauber calculations based on traditional models of nuclear physics. The transparency results suggest deviations from the traditional nuclear physics picture. The momentum transfer dependence of the measured nuclear transparency is consistent with Glauber calculations which include the quantum chromodynamics phenomenon of color transparency

[en] We present the first measurement of the Q²-dependence of the neutron spin structure function g₂ⁿ at five kinematic points covering 0.57 (GeV/c)² (le) Q² (le) 1.34 (GeV/c)² at x ∼ 0.2. Though the naive quark-parton model predicts g₂=0, non-zero values for g₂ occur in more realistic models of the nucleon which include quark-gluon correlations, finite quark masses or orbital angular momentum. The sensitivity of g₂ to physics beyond the simple quark-parton model provides a unique opportunity to examine QCD dynamics in nucleon structure. When scattering occurs from a non-interacting quark, a prediction for g₂ⁿ can be calculated using next-to-leading order fits to world data for g₁ⁿ. Our results show a positive deviation from this prediction indicating that contributions such as quark-gluon interactions may be important. Data were also obtained for g₁ⁿ and are consistent with a next-to-leading order fit to world data evolved to our kinematic range

[en] We present measurements of the recoil proton polarization for the d(polarized y, polarized p)n reaction at thetac.m. = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization py vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(y,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime

[en] We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from ⁴He at an average scattering angle θ_lab = 5.7 degrees and a four-momentum transfer Q² = 0.091 GeV². From these data, for the first time, the strange electric form factor of the nucleon G_E^s can be isolated. The measured asymmetry of A_PV = 6.72 ± 0.84 (stat) ± 0.21 (syst) parts per million yields a value of G_E^s = -0.038 ± 0.042 (stat) ± 0.010 (syst), consistent with zero

[en] We present the first measurements of (rvec e)p → epγ cross section in the deep virtual Compton scattering (DVCS) regime and the valence quark region (x_Bj = 0.36). From JLab E00-110, we extract the imaginary part of the Bethe-Heitler (BH)--DVCS interference terms, to order twist-3 for Q² = 1.5, 1.9, and 2.3 GeV², and the real part of the BH-DVCS interference terms at Q²2 = 2.3 GeV². We present the first model-independent measurement of linear combinations of generalized parton distributions (GPDs) and GPD integrals up to twist-3 approximation. The validity of this approximation is strongly supported by the absence of Q²-variation of the extracted terms--thereby constraining the size of higher twist contributions to our observables