Abstract:
The physics program in Hall A at Jefferson Lab commenced in the summer of 1997 with a detailed investigation of the 16O(e,e′p) reaction in quasielastic. constant (q,ω) kinematics at Q2≈0.8 (GeV/c)2, q ≈ 1 GeV/c, and ω≈445 MeV. Use of a self-calibrating, self-normalizing, thin-film waterfall target enabled a systematically rigorous measurement. Five-fold differential cross-section data for the removal of protons from the 1p-shell have been obtained for 0<p miss<350 MeV/c. Six-fold differential cross-section data for 0<Emiss<120 MeV were obtained for 0<pmiss<340 MeV/c. These results have been used to extract the ALT asymmetry and the RL, RT, RLT, and KL+TT effective response functions over a large range of Emiss and pmiss. Detailed comparisons of the 1p-shell data with Relativistic Distorted-Wave Impulse Approximation (RDWIA), Relativistic Optical-Model Eikonal Approximation (ROMEA). and Relativistic Multiple-Scattering Glauber Approximation (RMSGA) calculations indicate that two-body currents stemming from meson-exchange currents (MEC) and isobar currents (IC) are not needed to explain the data at this Q2. Further, dynamical relativistic effects are strongly indicated by the observed structure in ALT at pmiss≈300 MeV/c. For 25<Emiss<50 MeV and pmiss≈50 MeV/c. proton knockout from the 1s1/2-state dominates, and ROMEA calculations do an excellent job of explaining the data. However, as p miss increases, the single-particle behavior of the reaction is increasingly hidden by more complicated processes, and for 280<p miss<340 MeV/c, ROMEA calculations together with two-body currents stemming from MEC and IC account for the shape and transverse nature of the data, but only about half the magnitude of the measured cross section. For 50<Emiss<120 MeV and 145<pmiss<340 MeV/c, (e.e′pN) calculations which include the contributions of central and tensor correlations (two-nucleon correlations) together with MEC and IC (two-nucleon currents) account for only about half of the measured cross section. The kinematic consistency of the 1p-shell normalisation factors extracted from these data with respect to all available 16O(e, e′ p) data is also examined in detail. Finally, the Q2- dependence of the normalization factors is discussed.
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