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Interference Physics

Coordinators: John Arrington (johna@anl.org), Charles Hyde (hyde@jlab.org)

The effort of this sub-group is to consider the benefits of the application of polarized positrons in the electromagnetic physics sector. In the energy range currently available at JLab, ther is no specific difference with respect to the scientific information obtained with an electron or a positron probe. However, when more than one QED-based mechanism contributes to a reaction process, the comparison between lepton beams of opposite charge allows one to uniquely distinguish the quantum interference between these mechanisms. This feature is expressed in the experimental measurement of the electromagnetic form factors of the nucleon where two-photon exchange mechanisms may reconcile cross section and polarization data, and also in the experimental measurement of the generalized parton distributions of the nucleon where the interference between the Bethe-Heitler and virtual Compton amplitudes is a key observable.