Photopion Production at Higher Energies

Photopion production from a nucleon target is a fundamental process that is essential for studies of high-energy photoreactions in nuclei and for the study of quark models in the high energy regime. The approved JLAB experiment E94-104 uses a 6 GeV beam to investigate the constituent quark counting rule for the gamma n --> pi- p differential cross section. This measurement can be extended to 8 GeV as JLAB energies are upgraded. Quark model predictions for the momentum dependence of the ratio of pi- to pi+ photoproduction from the nucleon make their relative cross-section an important observable to investigate at high energies. Not only will it provide a decisive test of pion photoproduction models, but it is an excellent means of investigating the transition from a description based on nucleon-meson degrees of freedom to a QCD-based description in terms of quark-gluon degrees of freedom