The proton Compton effect has been studied in the region between the threshold for pion photoproduction and the Δ(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≤${\mathit{E}}_{\gamma }$≤289 MeV and for angles in the range 25°<${\mathrm{\theta }}_{\mathrm{lab}}$<135°. 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, α¯ and β¯. We find, subject to the dispersion sum rule constraint α¯+β¯=(14.2±0.5)×${10}^{\mathrm{-}4}$ ${\mathrm{fm}}^3$, that α¯=(9.8±0.4±1.1)×${10}^{\mathrm{-}4}$ ${\mathrm{fm}}^3$ and β¯=(4.4∓0.4∓1.1)×${10}^{\mathrm{-}4}$ ${\mathrm{fm}}^3$, which are consistent with the best previous measurements.

• Received 12 April 1993

DOI:https://doi.org/10.1103/PhysRevC.48.1497