A systematic analysis of microscopic nucleon-nucleus optical potential for p-Ni scattering

A microscopic proton-nucleus optical potential is calculated for all even isotopes ^52-112Ni within the Brueckner-Hartee-Fock framework. The reaction matrices calculated using three (Argonne v18, Reid93 and NijmII) realistic inter-nucleon potentials with and without three-body forces (Urbana IX (UVIX) and the density dependent three-nucleon interaction (TNI) model of Lagaris, Friedman and Pandharipande), have been folded over the neutron and proton density distributions of the relevant targets obtained by using the relativistic mean field approach. It is observed that the inclusion of both models of the three-body forces somewhat reduces the strength of the central part of the optical potential in the nuclear interior and affects only marginally the spin-orbit part of the potential. Further, the calculated volume integral of the real part of the spin-orbit optical potential as well as its peak value are found to decrease systematically with the addition of neutrons. The calculated optical potentials reproduce remarkably well the existing experimental differential cross section (dσ/dθ) and the polarization (Ay) data for p-^58-64Ni scattering at 39.6 and 65 MeV projectile energies. The inclusion of three-body forces (UVIX and TNI) does not lead to any change in the calculated observables (dσ/dθ and Ay) indicating that the p-Ni scattering data analyzed here are not sensitive to the nuclear interior. Identical observations are also found in the Zr, Sn and Pb isotopic chains. Therefore, these observed features of the microscopic optical potential seem general and may hold globally.