Energy Dependence of the Effective Interaction for Nucleon-Nucleus Scattering

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We have measured cross sections and analyzing powers for 40, 42, 44, 48Ca and 16O at IUCF using the new high-resolution K600 spectrometer for 100 and 200 MeV protons. Measurements at 318 MeV for 40, 42, 44 ,48Ca and 32 ,34S were done at LAMPF using the HRS spectrometer. In this work, we obtain empirical effective interactions by fitting inelastic scattering data for many low-lying normal-parity isoscalar excitations of the self-conjugate nuclei 16O and 40Ca, assuming a local tp folding model. One-nucleon transition densities are from (e, e') . The fitted interactions are iterated to generate optical potentials self-consistently. We find that the fitted parameters are essentially target independent, which supports the validity of the local density hypothesis. Elastic scattering is predicted by extracting the rearrangement factor (1 + pd/dp) from the fitted in elastic interactions. Below 300 MeV the strength of the empirical interaction is reduced at zero density and the general density dependence is weaker compared to the theoretical interaction. Above 300 MeV we find the density dependence is stronger than expected. The empirical interactions provide better descriptions of elastic and inelastic data than IA calculations or LDA calculations using theoretical G-matrices, and can be used for nuclear structure studies of other nuclei . Fitted optical potentials above 300 MeV are comparable to equivalent Schrödinger potentials from the relativistic IA2 model.