This project is analyzing data from experiments at the Los Alamos Meson Physics Facility (LAMPF) and the Indiana University Cyclotron Facility (IUCF) on nuclear structure with intermediate energy protons. These experiments are followed by a detailed numerical analysis of the data to compare with current models of the fundamental proton-nucleus interaction and nuclear structure. For this purpose, a number of large computer codes for use on the supercomputers have already been developed and modified.
Currently, there are three areas in which final (as yet unpublished) data requiring analysis have been determined. These are in measurements of elastic and inelastic proton cross sections and spin observables at several energies, scattering measurements on non-spherical nuclei to determine nuclear size and shape parameters, and two neutron pickup reactions to measure pairing correlations in nuclei.
Michael A. Franey, Research Associate
In the first case, primary interest is in the modification of the fundamental proton-proton and neutron interactions inside of the nuclear medium. This nuclear density dependence is fundamental to the theory of proton nucleus interactions and is of direct significance to astrophysical theories of the origin of the universe and the dynamics of neutron stars and black holes. The modification of the nucleon-nucleon interaction in nuclei is a manifestation of the underlying quark structure of nucleons.
In the second area, determinations of the nuclear shape parameters (quadrupole, octupole, hexadecapole, and higher) can be compared with modern Boson models for nuclear excitation modes.
In the last area, the experiments are very sensitive to the departures of the motion of individual nucleons in the nucleus from completely independent orbits (pairing correlations are the most important). The experiments can also give, upon analysis, information on the modifications discussed above of the nucleon-nucleon interaction when the nucleons interact in states of high angular momentum.
Previous work compared the cross sections and spin analyzing powers of 650 MeV protons on 206- and 208Pb with large basis shell model (Random Phase Approximation) calculations, using an effective nucleon-nucleon interaction derived from earlier analysis of the Pb elastic scattering data. The conclusions were that the shapes of the cross section data (scattering probability vs angle) were well represented by the theory, but that the magnitudes (normalization of data to theory) needed adjusting by factors of from 0.3 to 2.7 depending upon the particular nuclear excitation state. This indicates that the effective interaction needs slight adjusting or that the shell model space needs to be even larger.
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URL: http://www.msi.umn.edu/about/publications/annualreport/ar2000/depts/IT/PhysAstron/Physics/hintz.html |
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