Asymmetry dependence of proton correlations.

Department of Chemistry, Washington University, St Louis, MO 63130, USA.
Physical Review Letters (Impact Factor: 7.73). 11/2006; 97(16):162503. DOI: 10.1103/PHYSREVLETT.97.162503
Source: PubMed

ABSTRACT A dispersive-optical-model analysis of p+40Ca and p+48Ca interactions has been carried out. The real and imaginary potentials have been constrained from fits to elastic-scattering data, reaction cross sections, and level properties of valence hole states deduced from (e, e' p) data. The surface imaginary potential was found to be larger overall and the gap in this potential on either side of the Fermi energy was found to be smaller for the neutron-rich p+48Ca system. These results imply that protons with energies near the Fermi surface experience larger correlations with increasing asymmetry.

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    ABSTRACT: Single-neutron-transfer measurements using (p,d) reactions have been performed at 33 MeV per nucleon with proton-rich 34Ar and neutron-rich 46Ar beams in inverse kinematics. The extracted spectroscopic factors are compared to the large-basis shell-model calculations. Relatively weak quenching of the spectroscopic factors is observed between 34Ar and 46Ar. The experimental results suggest that neutron correlations have a weak dependence on the asymmetry of the nucleus over this isotopic region. The present results are consistent with the systematics established from extensive studies of spectroscopic factors and dispersive optical-model analyses of 40-49Ca isotopes. They are, however, inconsistent with the trends obtained in knockout-reaction measurements.
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    ABSTRACT: A survey of our present understanding of absolute spectroscopic factors near stable closed-shell nuclei is given based on our current interpretation of the (e, e'p) reaction. Uncertainties associated with the imprecise knowledge of the degree of nonlocality of the optical potential of the knocked out proton are identified. Theoretical expectations for the dependence of spectroscopic factors on the nucleon asymmetry are outlined. Conflicting results obtained from various reactions concerning the asymmetry dependence of spectroscopic factors are surveyed. The possibility of obtaining reliable absolute spectroscopic factors with reactions initiated by hadrons is discussed with special emphasis on present and future radioactive beam experiments. The combined and integrated analysis of such reactions using a Green's function framework in the form of an extended dispersive optical model may provide a useful approach to resolve this theoretical open problem.
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