Elastic pd Scattering at 316, 364, 470, and 590 MeV in the Backward Hemisphere

The results of an investigation of the elastic $\mathrm{pd}$ differential cross section for center-of-mass angles between 91 and 164\ifmmode^\circ\else\textdegree\fi{} at energies of 316, 364, 470, and 590 MeV are presented. For center-of-mass scattering angles larger than 130\ifmmode^\circ\else\textdegree\fi{}, the cross sections at any given angle are within 10% of each other for the three largest energies. The extrapolated 180\ifmmode^\circ\else\textdegree\fi{} differential cross section observed in this experiment remains nearly constant from 316 to 590 MeV. This is in marked contrast to the rapid decrease in cross section with increasing energy observed by other investigators for both larger and smaller energies. Possible theoretical explanations of this behavior are mentioned.