Measurement of proton polarization in the d(γ,p)n reaction

A proposal was approved by CEBAF PAC7 to measure angular distributions of the proton polarization for the d(γ,p)n reaction in the GeV region. This proposed measurement will test the validity of extensions of conventional nuclear-physics theories to the higher energy regime. The results of the experiment will further constrain the evidence from SLAC experiments NE8 and NE17 that asymptotic scaling was observed above a photon energy of 1.3 GeV. Photoproton polarization measurements at lower energy indicate that the magnitude of the polarization increases with energy. This is consistent with the observation that polarizations are large in high-energy processes, e.g. Ann in pp → pp scattering or Ay in pp → π0X. However, the polarizations in hadron-hadron scattering are believed to arise from Landshoff mechanisms. The higher energy photoproton experiment will permit the first measurements of polarization for a reaction, γd → pn, where there are no Landshoff terms. The experiment would make use of a polarimeter installed in either the High Resolution Spectrometer in Hall A or the Short Orbit Spectrometer in Hall C at CEBAF