216 research outputs found
Toward a Global Dispersive Optical Model for the Driplines
A dispersive-optical-model analysis has been performed for both protons and
neutrons on 40,42,44,48Ca isotopes. The fitted potentials describe accurately
both scattering and bound quantities and extrapolate well to other stable
nuclei.
Further experimental information will be gathered to constrain extrapolations
toward the driplines.Comment: Invited talk at the "10th International Conference on Nucleus-Nucleus
Collisions", Beijing, 16-21 August 200
Adding Corrections to Global Spherical Potentials for Use in a Coupled-Channel Formulation
The coupled-channel technique augments a non-relativistic distorted wave born
approximation scattering calculation to include a coupling to virtual states
from the negative energy region. It has been found to be important in low
energy nucleon-nucleus scattering. We modify the nucleon-nucleus standard
optical potentials, not designed for a coupled-channel space, so they can be
used in that setting. The changes are small and systematic. We use a standard
scattering code to adjust a variety of optical potentials and targets such that
the original fit to scattering observables are maintained as we incorporate the
coupled-channel environment. Overall over forty target nuclei were tested from
to and nucleon projectile energies from 1 MeV to 200 MeV. There
is excellent improvement in fitting the scattering observables, especially for
low energy neutron scattering.The corrections were found to be unimportant for
projectile energies greater than 200 MeV. The largest changes are to the
surface amplitudes while the real radii and the real central amplitude are
modified by only a few percent, every other parameter is unchanged. This
technique is general enough to be applied to a variety of inelastic theoretical
calculations.Comment: Second draft, not yet submitted to a journal in this for
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 O and Ca are
calculated as a function of energy from ~MeV laboratory energy with a
microscopic first order optical potential derived within the framework of the
Watson expansion. Although these results are already 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.Comment: 10 pages (Revtex 3.0), 6 fig
Full-Folding Optical Potentials for Elastic Nucleon-Nucleus Scattering based on Realistic Densities
Optical model potentials for elastic nucleon nucleus scattering are
calculated for a number of target nuclides from a full-folding integral of two
different realistic target density matrices together with full off-shell
nucleon-nucleon t-matrices derived from two different Bonn meson exchange
models. Elastic proton and neutron scattering observables calculated from these
full-folding optical potentials are compared to those obtained from `optimum
factorized' approximations in the energy regime between 65 and 400 MeV
projectile energy. The optimum factorized form is found to provide a good
approximation to elastic scattering observables obtained from the full-folding
optical potentials, although the potentials differ somewhat in the structure of
their nonlocality.Comment: 21 pages, LaTeX, 17 postscript figure
Sensitivities of the Proton-Nucleus Elastical Scattering Observables of 6He and 8He at Intermediate Energies
We investigate the use of proton-nucleus elastic scattering experiments using
secondary beams of 6He and 8He to determine the physical structure of these
nuclei. The sensitivity of these experiments to nuclear structure is examined
by using four different nuclear structure models with different spatial
features using a full-folding optical potential model. The results show that
elastic scattering at intermediate energies (<100 MeV per nucleon) is not a
good constraint to be used to determine features of structure. Therefore
researchers should look elsewhere to put constraints on the ground state wave
function of the 6He and 8He nuclei.Comment: To be published in Phys. Rev.
Application of Multiple Scattering Theory to Lower Energy Elastic Nucleon-Nucleus Reactions
The optical model potentials for nucleon-nucleus elastic scattering at
~MeV are calculated for C, O, Si, Ca,
Fe, Zr and Pb in first order multiple scattering theory,
following the prescription of the spectator expansion, where the only inputs
are the free 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.Comment: 12 pages (Revtex 3.0), 7 fig
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