COMPTON-SCATTERING FROM THE PROTON

The proton Compton effect has been studied in the region between the threshold for pion photoproduction and the DELTA(1232). The measurements were performed using bremmstrahlung from the high duty-factor electron beam available at the Saskatchewan Accelerator Laboratory. Elastically scattered photons were detected with an energy resolution of approximately 1.5% using a large NaI total absorption scintillation detector. Differential cross sections were measured for photon energies in the range 136 MeV less-than-or-equal-to E(gamma) less-than-or-equal-to 289 MeV and for angles in the range 25-degrees < theta(lab) < 135-degrees. The angular distributions and the excitation functions derived from these data are in agreement with recent theoretical analyses. The results were interpreted within a formalism based in part on dispersion relations to obtain model-dependent estimates of the electric and magnetic polarizabilities, alphaBAR and betaBAR. We find, subject to the dispersion sum rule constraint alphaBAR + betaBAR=(14.2+/-0.5)X10(-4) fm3, that alphaBAR=(9.8+/-0.4+/-1.1)X10(-4) fm3 and betaBAR=(4.4-/+0.4-/+1.1)X10(-4) fm3, which are consistent with the best previous measurements.