[en] The parity-violating asymmetry in e-²H deep inelastic scattering (DIS) can be used to extract the weak neutral-current coupling constants C_2q. A measurement of this asymmetry at two Q² values is planned at Jefferson Lab. Results from this experiment will provide a value of 2C_2u-C_2d to a precision of ± 0.03, a factor of eight improvement over our current knowledge. If all hadronic effects can be understood, this results will provide information on possible extensions of the Standard Model, complementary to other experiments dedicated to new physics searches. Presented here are the physics motivation, experimental setup, potential hadronic effects and their implications, and the future of PV DIS at Jefferson Lab

[en] The authors present here recent progress on the experimental study of the neutron spin structure at Jefferson Lab Hall A. They focus on two precision experiments. The physics motivation and the experimental setup will be described first. Then they present results for the neutron spin asymmetry A₁ⁿ and results for spin-flavor decomposition of the nucleon spin in the valence quark region, and preliminary results for the neutron spin structure function g₂ⁿ at low Q²

[en] This dissertation will first give an introduction to the theories and formalism of polarized deep inelastic scattering and a review of the theories of A1n. Next the experiment E99-117 at JLab Hall A will be described, followed by the data analysis. The data presented greatly improve the current world fit of neutron polarized structure functions and provide valuable insight in the understanding of the neutron spin structure

[en] We have measured the neutron spin asymmetry A₁ⁿ with high precision at three kinematics in the deep inelastic region at x = 0.33, 0.47 and 0.60, and Q² = 2.7, 3.5 and 4.8 (GeV/c)², respectively. Our results unambiguously show, for the first time, that A₁ⁿ crosses zero around x = 0.47 and becomes significantly positive at x = 0.60. Combined with the world proton data, polarized quark distributions were extracted. Our results, in general, agree with relativistic constituent quark models and with perturbative quantum chromodynamics (pQCD) analyses based on the earlier data. However they deviate from pQCD predictions based on hadron helicity conservation

[en] Parity violating electron scattering has become a well established tool which has been used, for example, to probe the Standard Model and the strange-quark contribution to the nucleon. While much of this work has focused on elastic scattering, the RES-Parity experiment, which has been proposed to take place at Jefferson Laboratory, would focus on inelastic scattering in the low-Q², low-W domain. RES-Parity would search for evidence of quark-hadron duality and resonance structure with parity violation in the resonance region. In terms of parity violation, this region is essentially unexplored, but the interpretation of other high-precision electron scattering experiments will rely on a reasonable understanding of scattering at lower energy and low-W through the effects of radiative corrections. RES-Parity would also study nuclear effects with the weak current. Because of the intrinsic broad band energy spectrum of neutrino beams, neutrino experiments are necessarily dependent on an untested, implicit assumption that these effects are identical to electromagnetic nuclear effects. RES-Parity is a relatively straight forward experiment. With a large expected asymmetry (∼ 0.5 x 10^-4) these studies may be completed with in a relatively brief period

[en] A high-resolution (σ_instr. = 1.5 MeV) search for narrow states (Λ < 10 MeV) with masses of M_x ∼ 1500-1850 MeV in ep → e' K⁺ X, e' K^- X and e' π⁺ X electroproduction at small angles and low Q² was performed. These states would be candidate partner states of the reported Θ⁺(1540) pentaquark. No statistically significant signal was observed in any of the channels at 90% C.L. Upper limits on forward production were determined to be between 0.7% and 4.2% of the Λ(1520) production cross section, depending on the channel and the assumed mass and width of the state

[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 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