Precise single-scattering optical-potential fit to 1-GeV p-4He elastic scattering

Using a relativistic form for the relation between the nucleon-nucleon scattering amplitude and the scattering operator, a single-scattering nucleon-nucleus optical potential is found which gives a precise fit with no adjustable parameters to the small-angle scattering of protons on ⁴He at 1-GeV incident lab energy. The method then allows a determination of the ratio of real to imaginary nucleon-nucleon forward-scattering amplitudes at other energies such as 600 MeV.