Ratios of the real to imaginary part of the p{sup 4}He and pn elastic scattering amplitudes at 0.7 GeV

The ratios ρ p He and ρ pn of the real to imaginary part of the forward proton-4He and proton-neutron elastic scattering amplitudes have been determined from the data on proton-helium elastic scattering cross sections at 0.7 GeV in the Coulomb-nuclear interference region to be ρ p He =−0.06±0.06 and ρ pn = −0.28±0.12. The existing experimental values of ρ p He are compared in a wide range of energies with the corresponding values calculated by means of the Glauber model using the ratios ρ pp and ρ pn evaluated with the help of the dispersion relations.