Colloquia

The quark and gluon structure of the nucleons (protons and neutrons) was established by illuminating atomic nuclei with high energy unpolarized real and virtual photons. The interactions between quarks follow "scaling" rules that were also established with unpolarized photons. With polarized photons it is possible to explore the nucleon structure even further. Polarized photons have been used to determine that quarks carry only 1/3 of the spin, but the distribution of spin among types ("flavors") of quarks is still under study. And the "missing" spin carriers are still being investigated. The interactions between quarks and gluons have barely been explored experimentally. Polarized photons can also uncover the details of those interactions and relate them to calculations based on Quantum Chromodynamics - QCD, the fundamental theory of strong interactions. There is an extensive program of nucleon structure studies with polarized photons and polarized nuclear targets at Jefferson Lab with the goal of answering some of these and other related questions. Highlights of the Hall C component of this program will be presented.