A GLOBAL NUCLEON OPTICAL-MODEL POTENTIAL

We describe a new parametrization of the nucleon-nucleus optical-model potential based on data for A = 40 to 209, proton energies of 16 to 65 MeV and neutron energies of 10 to 26 MeV, including extensive polarized-beam data. This parametrization, called CH89, is based on the current understanding of the basis of the optical potential, such as the folding model and nuclear matter approaches. It differs significantly from previous global parametrizations, especially in the weakness of the isovector potential, the parametrization of potential radii, and the smooth variation of imaginary-potential depths with energy. We also describe an optical-model parameter search system, MINOPT, based on the minimization program MINUIT. It is applied to analyze simultaneously a large database of nearly 300 carefully selected angular distributions. Parameter uncertainties and correlations between parameters are estimated by using the non-parametric statistical technique known as the bootstrap method. CH89 is intended to serve as a starting point for definitive tests of models of the nucleon-nucleus interaction, and to be of immediate use for applications.