[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 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