The Quest for Two Photon Exchange in Electron Scattering

Dr. Bo Zhao
Jefferson National Accelerator Facility

Over nearly half a century much information on nucleon and nuclear structure has been obtained through the study of electron scattering experiments in which the one photon exchange approximation is assumed.  In recent years, as new high precision data on cross section and polarization observables become available, two photon exchange is found to have sizable contributions to some observables measured from the electron scattering, for example, the ratio of elastic proton form factors GpE/GpM.  In this talk, I will discuss the theoretical predictions and experimental results on two photon exchange and look forward to the new study in the future.