An optical model analysis of the __Ca(p,p) __Ca reaction in the energy range r-22 MeV

A study has been undertaken to describe differential cross section, total reaction cross section, and polarization data for protons elastically scattered by 40Ca over the bombarding energy range of 4-22 MeV in terms of an Optical Model. It has been found that this model, involving 10 parameters to specify the geometry and strengths of the coulomb, real, imaginary, and spin-orbit wells, furnishes an adequate description of the scattering data. In the energy region below the (p,n) threshold (15.5 MeV), compound elastic scattering contributes a sizeable fraction (-20%) of the average differential cross section. To accommodate this contribution in the calculation requires a change in the geometry of the surface imaginary and spin-orbit wells. The strength parameter of the nuclear potential wells was allowed to vary at each energy to optimize the fit to the data. This procedure yielded energy dependences of the real central and surface imaginary wells of The spin-orbit strength was relatively constant at approximately 5 MeV over the range of bombarding energies above 8 MeV. In the 5-8 MeV region isolated, high resolution angular distributions constitute the bulk of available data. This coupled with an apparently large compound elastic contribution, prevented a continuation of the systematic fitting procedure used in the higher energy region. An attempt has been made to provide a description of the compound elastic contribution utilizing a Hauser-Feshbach calculation and empirical treatments of the scattering data. It is hoped that such a description of the compound term will allow a continuous Optical Model parameter set, describing the shape elastic process, to be determined. [see PDF for formulas