Syed Rafi

MICROSCOPIC NEUTRON OPTICAL POTENTIAL IN THE ENERGY REGION 65–225 MeV

In the present work, we report a microscopic optical potential analysis of the extensive neutron elastic scattering data from 12C, 40Ca and 208Pb in the 65–225 MeV energy region. Brueckner–Hartree–Fock method has been used to calculate the optical potential, where one requires internucleon potential to calculate reaction matrices which are then folded over the nucleon densities in the target nuclei. We report the predictions of the calculated potential using Argonne v-18 and Urbana v-14 local nucleon–nucleon potentials. The modern potential v-18 has been used for the first time to calculate the nucleon–nucleus optical potential. We also compare our predictions with the empirical potentials. The results indicate that the predictions of our microscopic potential are in better agreement with the experimental data as compared with the empirical global optical potentials.

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.

EXACT CALCULATION OF THE DIRECT PART OF THE NUCLEON–NUCLEUS SPIN-ORBIT POTENTIAL IN BRUECKNER THEORY

We have shown that the commonly used series expansion given by Greenlees et al. and Scheerbaum for calculating the spin-orbit potential is not rapidly convergent and that exact calculation of the dominant direct part can be easily done. Our exact calculation of the microscopic optical potential for the scattering of protons from 40Ca and 208Pb at 65 MeV and 200 MeV shows that the direct part is substantially different from the results using series expansion. Our results show that the spin-orbit potential affects the cross-section even at intermediate angles specially at high energies. The results presented here have direct application for calculating spin-orbit potential of all strongly interacting Fermionic probes.

MICROSCOPIC OPTICAL POTENTIAL FROM ARGONNE INTER-NUCLEON POTENTIALS

In the present work we describe our results concerning the calculation of equation of state of symmetric zero temperature nuclear matter and the microscopic optical potential using the soft-core Argonne inter-nucleon potentials in first order Brueckner–Hartree–Fock (BHF) theory. The nuclear matter saturates at a density 0.228 nucleon/fm3 with 17.52 MeV binding energy per nucleon for Argonne av-14 and at 0.228 nucleon/fm3 with 17.01 MeV binding energy per nucleon for Argonne av-18. As a test case we present an analysis of 65 and 200 MeV protons scattering from 208Pb. The Argonne av-14 has been used for the first time to calculate nucleon optical potential in BHF and analyze the nucleon scattering data. We also compare our reaction matrix results with those using the old hard-core Hamada–Johnston and the soft-core Urbana uv-14 and Argonne av-18 inter-nucleon potentials. Our results indicate that the microscopic potential obtained using av-14 gives marginally better agreement with the experimental data than the other three Hamiltonians used in the present work.