At high energies the property of QCD known as asymptotic freedom, which causes quarks to interact very weakly at short distances, allows for an efficient description in terms of quarks and gluons, or partons. In contrast, at low energies the effects of confinement imply a more efficient description in terms of mesons and baryons, or hadrons. Despite this apparent dichotomy, a striking similarity between data measured at high and low energies is observed. This is referred to as quark-hadron duality. Data accumulated at JLab have shown that such quark-hadron duality occurs at much lower values of momentum transfer, in more observables, and in far less limited regions of energy than hitherto believed. As a corollary, the quark parton model, developed to describe high-energy deep-inelastic scattering data, has been found to be remarkably successful in describing data at incident energies of order 5 GeV. With the 12-GeV JLab Upgrade, this will then in turn allow for a rich field of investigations in the valence quark region. An overview will be given of the JLab data to both study the quark-hadron duality phenomenon and quantify global and local aspects for duality, and the implications for the microscopic origins of duality in Quantum ChromoDynamics and our understanding of the strong force at large distances, comparable to the size of hadrons (~1 fm).
ANL Physics Division Colloquium Schedule