Large-angle proton-nucleus scattering shows no evidence for intermediateΔstates

It has been suggested that the discrepancy between data for large-angle proton-nucleus elastic scattering at 200 MeV and standard optical model interpretations can be explained by the formation of intermediate $\Delta$ isobars. To test this hypothesis we have carried out a measurement of the elastic scattering cross section for 300 MeV protons from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ for momentum transfers up to 6.8 ${\mathrm{fm}}^{-1\mathrm{}}$. Although the energy was chosen to match the resonance energy for $\Delta$ production, no need for corrections to a simple optical model, and thus no experimental evidence for intermediate $\Delta$ isobars, was found.