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 ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ 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.

• Received 16 April 1973

DOI:https://doi.org/10.1103/PhysRevLett.30.1257