Exact calculation of a microscopic nucleon spin-orbit potential: Reexamination of Brieva-Rook localization

Brieva-Rook approximations for calculating the equivalent local microscopic nucleon-nucleus spin-orbit potential has been examined in the energy region of 65<E<500MeV. We present an exact method for calculating both the direct and the exchange parts of the spin-orbit potential. It has been shown that the series expansion used earlier overestimates both the real and the imaginary parts by about 50%. Our results show that the exchange contribution to the total spin-orbit potential at low energies is only 15% (much smaller than earlier estimates) and becomes negligible around 200-MeV nucleon incident energy. Predictions of the new spin-orbit potential with minor scaling has been found to be in fair agreement with p-Pb208 scattering observables from 65 to 500 MeV.