Douglas Hasell
MIT
Recent, precise measurements of the proton form factor ratio performed using the polarized techniques show a striking discrepancy with measurements using the traditional, Rosenbluth separation technique. The common explanation to resolve this discrepancy is that hard, two-photon exchange is responsible. While soft, two-photon exchange is generally included in the radiative corrections; hard two-photon exchange is difficult to calculate and depends on models for the intermediate nucleon state. This presentation will give a brief overview of the observed discrepancy and of three recent experiments that measured the hard two-photon contribution in elastic electron-proton scattering. The results will be presented and compared to some theoretical and phenomenological calculations followed by some discussion and suggestions for future action.
LGRT 419B