Energy dependence of the relativistic impulse approximation for proton-nucleus elastic scattering

Results of relativistic and nonrelativistic impulse approximation calculations are compared for p+${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ elastic scattering observables between 181 and 1040 MeV. At 400 MeV and above, the relativistic approach is superior, especially with regard to spin observables. Below 400 MeV, neither calculation agrees well with experiment.