Nuclear physics with intermediate energy electrons

Nuclear physics is the study of strongly interacting matter and of the forces which govern its structure and dynamics. The goal of this paper is to give an understanding of nuclei as quantal many-body systems and of the nature of the strong force, ultimately in terms of the presumed underlying theory of quantum chromodynamics. The latter task will require a deeper understanding of hadron structure and of color confinement and, in turn, will provide the basis for exploring the structure of matter under extreme conditions, such as very high density or temperature. This program covers a very broad range of phenomena, theoretical concepts, and experimental tools and is reflected in the diverse degrees of freedom invoked in various contexts. This is indicated where degrees of freedom loosely identified with successively smaller distance scales are indicated. Very importantly, theoretical bridges have been built between the phenomenological descriptions associated with each set of degress of freedom. The mean field, determined self-consistently from the interactions of nucleons in quantum orbits, provides the basis for much of the authors microscopic understanding of nuclear structure and of our characterization of nuclear scattering processes. However, the authors are only beginning to address quantitatively the physics associated with short-range correlations, physics which takes us beyond the mean field description. The nuclear force has a very successful semi-phenomenological description in terms of hadronic degrees of freedom, both mesons and nucleon isobars. More problematic, of course, is our understanding of hadron structure and dynamics in terms of QCD