Results from CEBAF experiment E89-012: Measurements of deuteron photo-disintegration up to 4 GeV

The first measurements of differential cross sections for deuteron photo-disintegration at photon energies up to 4 GeV were performed at the Thomas Jefferson National Accelerator Facility early in 1996. Cross section results for D(γ,p)n at proton center of mass angle of 35°, 53° and 90° will be presented. These results are in good agreement with previous measurements at low energy and extend to higher energies where data were previously unavailable. The 90° degree data show behavior consistent with the constituent counting rules up to 4 GeV and are also in fair agreement with the asymptotic meson exchange model. The 37° and 53° data do not show clear signs of counting rule behavior, although a threshold in transverse momentum for the onset of scaling cannot be excluded.