Ratios of the real to imaginary part of the p4He and pn elastic scattering amplitudes at 0.7 GeV

The ratios ρpHe and ρpn 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 ρpHe =-0.06±0.06 and ρpn = -0.28±0.12. The existing experimental values of ρpHe are compared in a wide range of energies with the corresponding values calculated by means of the Glauber model using the ratios ρpp and ρpn evaluated with the help of the dispersion relations.