Studies of hadronic structure using electromagnetic probes

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One of the central problems of modern physics concerns our understanding of the building blocks of the atomic nucleus: the nucleons (protons and neutrons), and particles (mesons) that bind them. Notable discoveries have indicated that mesons and nucleons consist of yet more fundamental constituents, the quarks and gluons. As a result of the motion of the quarks (which produces magnetism) and their electrical charge, mesons and nucleons exhibit a distinct structure. While a very good theoretical framework (called Quantum ChromoDynamics, or QCD) is able to accurately describe how quarks and gluons interact at extremely high energies (or, equivalently, when the quarks are very close together), it has been extremely difficult to apply QCD to lower energy (larger distance) phenomena. The paradox is that the increasing complexity of the quark-gluon interaction as quarks get further apart is critically important to their confinement within mesons and nucleons, but this complexity greatly limits our ability to perform the QCD calculations needed to confirm our understanding. One of the obstacles to our improved comprehension has been a lack of quality data, particularly for the Deep Exclusive electron scattering reactions where the system responds coherently to the incoming probe, and so provides the clearest picture of the inner workings of QCD. These measurements are technically challenging and only now are made feasible with recent advances in accelerator and detector technology, as enabled by the ongoing upgrade of Jefferson Lab Hall C. Dr. Huber leads several experiments, such as Measurements of the Charged Pion Form Factor and QCD Factorization Studies of Exclusive pi+ and K+ Production, which show particular promise to our understanding of the underlying quark/gluon dynamics and provide valuable input to the interpretation of other experiments. By making precision measurements of this nature, we hope to better understand the short-long range transition of QCD, and better make the elusive connection between the underlying quark/gluon dynamics and the observed structures of mesons and nucleons.