[en] At the Thomas Jefferson National Accelerator Facility, we have studied the elastic scattering of polarized electrons from hydrogen. The resulting parity-violating electroweak asymmetry is sensitive to the contributions of strange quarks to the nucleon form factors at a level that is of theoretical interest. Using events at a laboratory scattering angle of 12.3^o and (Q²)=0.477 GeV/c, we measure the linear combination of strange form factors (Gⁿ_E) + 0.39G^E_M/(G^py_M/mu_p) = 0.091+/-0.054+/-0.039, where the first error is the quadratic sum of our systematic and statistical errors and the second error is due to uncertainty in nucleon form factors

[en] A series of bench-scale experiments were completed to evaluate acid gases of HCl, SO₂, and SO₃ on mercury oxidation across a commercial selective catalytic reduction (SCR) catalyst. The SCR catalyst was placed in a simulated flue gas stream containing O₂, CO₂, H₂O, NO, NO₂, and NH₃, and N₂. HCl, SO₂, and SO₃ were added to the gas stream either separately or in combination to investigate their interactions with mercury over the SCR catalyst. The compositions of the simulated flue gas represent a medium-sulfur and low- to medium-chlorine coal that could represent either bituminous or subbituminous. The experimental data indicated that 5-50 ppm HCl in flue gas enhanced mercury oxidation within the SCR catalyst, possibly because of the reactive chlorine species formed through catalytic reactions. An addition of 5 ppm HCl in the simulated flue gas resulted in mercury oxidation of 45% across the SCR compared to only 4% mercury oxidation when 1 ppm HCl is in the flue gas. As HCl concentration increased to 50 ppm, 63% of Hg oxidation was reached. SO₂ and SO₃ showed a mitigating effect on mercury chlorination to some degree, depending on the concentrations of SO₂ and SO₃, by competing against HCl for SCR adsorption sites. High levels of acid gases of HCl (50 ppm), SO₂ (2000 ppm), and SO₃ (50 ppm) in the flue gas deteriorate mercury adsorption on the SCR catalyst. (author)

[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 have measured the transverse asymmetry from inclusive scattering of longitudinally polarized electrons from polarized ³He nuclei at quasi-elastic kinematics in Hall A at Jefferson Lab with high statistical and systematic precision. The neutron magnetic form factor was extracted based on Faddeev calculations with an experimental uncertainty of less than 2%

[en] We have measured the transverse asymmetry A_T' in the quasi-elastic ³/rvec He/(/rvec e/,e') process with high precision at Q²-values from 0.1 to 0.6 (GeV/c)². The neutron magnetic form factor G_Mⁿ was extracted at Q²-values of 0.1 and 0.2 (GeV/c)² using a non-relativistic Faddeev calculation which includes both final-state interactions (FSI) and meson-exchange currents (MEC). Theoretical uncertainties due to the FSI and MEC effects were constrained with a precision measurement of the spin-dependent asymmetry in the threshold region of ³/rvec He/(/rvec e/,e'). We also extracted the neutron magnetic form factor G_Mⁿ at Q²-values of 0.3 to 0.6 (GeV/c)² based on Plane Wave Impulse Approximation calculations

[en] We present the first precision measurement of the spin-dependent asymmetry in the threshold region of ³He(e,e(prime)) at Q²-values of 0.1 and 0.2 (GeV/c)². The agreement between the data and non-relativistic Faddeev calculations which include both final-state interactions (FSI) and meson-exchange currents (MEC) effects is very good at Q² = 0.1 (GeV/c)², while a small discrepancy at Q² = 0.2 (GeV/c)² is observed

[en] We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from protons. Significant contributions to this asymmetry could arise from the contributions of strange form factors in the nucleon. The measured asymmetry is A = -15.05 ± 0.98(stat) ± 0.56(syst) ppm at the kinematic point <θ_lab> = 12.3^o and < Q²> = 0.477 (GeV/c)². Based on these data as well as data on electromagnetic form factors, we extract the linear combination of strange form factors G_E^s + 0.392G_M^s = 0.014 ± 0.020 ± 0.010 where the first error arises from this experiment and the second arises from the electromagnetic form factor data. This paper provides a full description of the special experimental techniques employed for precisely measuring the small asymmetry, including the first use of a strained GaAs crystal and a laser-Compton polarimeter in a fixed target parity-violation experiment

[en] We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The result is A = -15.05 +- 0.98(stat) ± 0.56(syst) ppm at the kinematic point theta_lab = 12.3 degrees and Q² = 0.477 (GeV/c)². The measurement implies that the value for the strange form factor (G_E^s + 0.392 G_M^s)/(G_M^p μ_p) = 0.069 +- 0.056 +- 0.039, where the first error is experimental and the second arises from the uncertainties in electromagnetic form factors. This measurement is the first fixed-target parity violation experiment that used either a ''strained'' GaAs photocathode to produce highly polarized electrons or a Compton polarimeter to continuously monitor the electron beam polarization