Electron Scattering from Nuclei at Several GeV

Abstract

A basic goal of physics is to uncover and then explain the layers in the structure of matter. In the last decade evidence has accumulated from experiments at GeV energies that nucleons and mesons are composed of a new substructure containing charged pointlike quarks interacting by gluon exchange. This is a peculiar substructure. The quarks and gluons carry a new quantum number called color, but they have never been observed isolated in the laboratory. The objects observed in real experiments appear to be combinations of quarks bound into color neutral particles or color singlets. Quantum chromo-dynamics (QCD) is the gauge theory of colored quarks and gluons invented to describe this substructure. A central task of modern nuclear physics is to understand how the structure and interactions of nucleons arise from the interactions among quarks.