Probing nucleons with photons at the quark level
  The description of electromagnetic interactions with hadrons from the quark level requires knowledge of the underlying quark-gluon ingredients. I discuss some properties of the quark-photon vertex and quark Compton vertex, along with the role of electromagnetic gauge invariance and vector-meson dominance. A simple parametrization for the quark-photon vertex is given. 
Gernot Eichmann
nucl-th hep-ph