Hall A,

These spectrometers will be utilized for detailed investigations of the structure of nuclei, mainly using the (e,ep) and (,e) reactions. These measurements will extend the range of momentum transfers and internal nucleon momenta well beyond the presently-known region. Such measurements could reveal the limitations of the conventional (and presently adequate) picture of nuclear structure based on nucleons interacting via meson exchange. Experiments of this type in heavy nuclei will expand our understanding of nuclear structure and provide information on how the nucleon's properties change when it is embedded in the nuclear medium. In few-body systems, where exact calculations can be performed for interacting nucleons, these experiments may reveal the complete breakdown of the meson exchange picture. More realistically, one will probably discover that at some point quark models will simply offer a much more economical description.

The elastic, inelastic, and weak structure of the nucleon is an important component of the Hall A program. The HRS spectrometers will be used to study the charge and magnetic form factors of the nucleons with greater accuracy than is currently available. A detailed study of spin observables in the transition will be performed. The strange-quark contributions to the charge and magnetization distributions of the nucleons will be investigated via very precise parity-violating electron scattering experiments using both H and He targets. Because He is a J=0, T=0 system, it has only a monopole charge form factor, and the electric strangeness contribution is probed directly. Such experiments will be stringent tests for microscopic models of the nucleon.