C. R. Chinn

Mean-field description of ground-state properties of drip-line nuclei: Pairing and continuum effects

Ground-state properties of exotic even-even nuclei with extreme neutron-to-proton ratios are described in the framework of self-consistent mean-field theory with pairing formulated in coordinate space. This theory properly accounts for the influence of the particle continuum, which is particularly important for weakly bound systems. The pairing properties of nuclei far from stability are studied with several interactions emphasizing different aspects, such as the range and density dependence of the effective interaction. Measurable consequences of spatially extended pairing fields are presented, and the sensitivity of the theoretical predictions to model details is discussed. {copyright} {ital 1996 The American Physical Society.}

Propagator modifications in elastic nucleon-nucleus scattering within the spectator expansion.

The theory of the elastic scattering of a nucleon from a nucleus is presented in the form of a spectator expansion of the optical potential. Particular attention is paid to the treatment of the free projectile-nucleus propagator when the coupling of the struck target nucleon to the residual target must be taken into consideration. First order calculations within this framework are shown for neutron total cross sections and for proton scattering for a number of target nuclides at a variety of energies. The calculated values of these observables are in very good agreement with measurement.

Application of multiple scattering theory to lower-energy elastic nucleon-nucleus scattering

The optical model potentials for nucleon-nucleus elastic scattering at 65 meV are calculated for [sup 12]C, [sup 16]O, [sup 28]Si, [sup 40]Ca, [sup 56]Fe, [sup 90]Zr, and [sup 208]Pb in first-order multiple scattering theory, following the prescription of the spectator expansion, where the only inputs are the free nucleon-nucleon (NN) potentials, the nuclear densities, and the nuclear mean field as derived from microscopic nuclear structure calculations. These potentials are used to predict differential cross sections, analyzing powers, and spin rotation functions for neutron and proton scattering at 65 MeV projectile energy and compared with available experimental data. The theoretical curves are in very good agreement with the data. The modification of the propagator due to the coupling of the struck nucleon to the residual nucleus is seen to be significant at this energy and invariably improves the congruence of theoretical prediction and measurement.

Correlations in a many-body calculation of {sup 11}Li

A many-body calculation of {sup 11}Li is presented where the only input is the well-tested, finite-range {ital D}1{ital S} effective interaction of {ital Gogny}. The nucleus ground state is modeled as a GCM configuration mixing of Hartree-Fock-Bogolyubov states generated with a constraint on the mean square radius. Pairing correlations are computed from the two-body interaction itself. The kinds of correlations included in this way are found to play an important role in describing the large {sup 11}Li radius. A substantive underlying {sup 9}Li core of {sup 11}Li is found, which has a different density profile than a free {sup 9}Li nucleus. The relations of this work with other approaches are discussed.

Total cross sections for neutron scattering

Measurements of neutron total cross sections are both extensive and extremely accurate. Although they place a strong constraint on theoretically constructed models, there are relatively few comparisons of predictions with experiment. The total cross sections for neutron scattering from [sup 16]O and [sup 40]Ca are calculated as a function of energy from 50 to 700 MeV laboratory energy with a microscopic first-order optical potential derived within the framework of the Watson expansion. Although these results are aleady in qualitative agreement with the data, the inclusion of medium corrections to the propagator is essential to correctly predict the energy dependence given by the experiment. In the region between 100 and 200 MeV, where off-shell [ital t][rho] calculations for both [sup 16]O and [sup 40]Ca overpredict the experiment, the modification due to the nuclear medium reduces the calculated values. Above 300 MeV these corrections are very small and depending on the employed nuclear mean field tend to compensate for the underprediction of the off-shell [ital t][rho] results.

Role of final state interactions in quasielastic 56Fe(e,e') reactions at large ||q

A relativistic finite nucleus calculation using a Dirac optical potential is used to investigate the importance of final state interactions (FSI) at large momentum transfers in inclusive quasielastic electronuclear reactions. The optical potential is derived from first-order multiple scattering theory and then is used to calculate the FSI in a nonspectral Greens function doorway approach. At intermediate momentum transfers excellent predictions of the quasielastic [sup 56]Fe([ital e],[ital e][prime]) experimental data for the longitudinal response function are obtained. In comparisons with recent measurements at [vert bar][ital [rvec q]][vert bar]=1.14 GeV/[ital c] the theoretical calculations of [ital R][sub [ital L]] give good agreement for the quasielastic peak shape and amplitude, but place the position of the peak at an energy transfer of about 40 MeV higher than the data.

The Role of Final State Interactions in Quasielastic

A relativistic finite nucleus calculation using a Dirac optical potential is used to investigate the importance of final state interactions (FSI) at large momentum transfers in inclusive quasielastic electronuclear reactions. The optical potential is derived from first-order multiple scattering theory and then is used to calculate the FSI in a nonspectral Greens function doorway approach. At intermediate momentum transfers excellent predictions of the quasielastic [sup 56]Fe([ital e],[ital e][prime]) experimental data for the longitudinal response function are obtained. In comparisons with recent measurements at [vert bar][ital [rvec q]][vert bar]=1.14 GeV/[ital c] the theoretical calculations of [ital R][sub [ital L]] give good agreement for the quasielastic peak shape and amplitude, but place the position of the peak at an energy transfer of about 40 MeV higher than the data.