Nonperturbative Behavior of Quarks [Book Chapter]

Several experiments have established that quarks exhibit different aspects of their interactions depending on their environment when they are probed. The nonlinear behavior found in nuclei is treated by expanding the many quark nuclear state as a series in color singlet multiquark states. The effects found in numerous nuclear target experiments can all be described by including the first two terms in this multiquark expansion. Comparisons with data from deep inelastic scattering by electrons, muons, neutrinos and antineutrinos will be given and also comparisons with dimuon production by protons on nuclei will be examined. Dilepton depletion at small target parton momentum fraction in proton-nucleus collisions will also be discussed as an example of this nonlinear behavior.