Proton Compton Scattering at 0.55-to-4.5-GeV Energy and 0.12-to-1.0-(GeV/c)2Momentum Transfer

Results are presented on the elastic scattering of photons by protons. The incident photon energy ranged from 0.55 GeV to 4.5 GeV, and the four-momentum transfer $t$ ranged from 0.12 to 1.0 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. The data at large angles, $60°<{\theta }^{*}<115\mathrm{}°$, are characterized by a pronounced excitation of the $D_{13}\mathrm{}\left(1518\right)\mathrm{}$ resonance, a shoulder in the 1688-MeV mass region, and a precipitous drop thereafter in the cross section as a function of incident energy. The low-$t$ data are characterized by a diffraction slope of 5 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{-2\mathrm{}}$. The data are inconsistent with the predictions of the vector-dominance model if the latter is restricted to ${\rho }^0$, $\omega$, and $\phi$ vector mesons.