Absolute differential cross section measurements for proton-deuteron elastic scattering at 641. 3 and 792. 7 MeV

The absolute {ital p}-{ital d} elastic-scattering differential cross sections were measured at 641.3 and 792.7 MeV beam energies over a range of c.m. angles from {similar to}35{degree} to {similar to}115{degree} and {similar to}35{degree} to {similar to}140{degree}, respectively. The longitudinally polarized ({ital L}-type) proton beam produced by the Lamb-shift ion source at LAMPF was used. The beam intensity was measured to high accuracy ({similar to}0.1%) by a scintillator-beam particle-counting system designed and developed prior to the experiment. Typical uncertainties in the absolute cross sections were about 2--3% total, somewhat larger at back angles. The present results were compared with the existing measurements and the controversy about the previous data at 800 MeV was resolved. The present data can be fit with a relativistic multiple-scattering theory which uses off-mass-shell extrapolations of the nucleon-nucleon amplitudes suggested by the structure of derivative meson-nucleon couplings. Relativistic-impulse-approximation calculations do not fit these data at either energy.