Polarization Measurements in High-Energy Deuteron Photodisintegration

We present measurements of the recoil proton polarization for the $d(\overrightarrow{\gamma },\overrightarrow{p})n$ reaction at ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=90\mathrm{}°$ for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization $p_y$ vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer $C_x$ does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the $d(\gamma ,p)n$ cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.