[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 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