dorsal/arxiv
View SchemaInsensitivity of the elastic proton-nucleus reaction to the neutron radius of 208Pb
| Authors | J. Piekarewicz, S. P Weppner |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/0509019 |
| URL | https://arxiv.org/abs/nucl-th/0509019 |
| DOI | 10.1016/j.nuclphysa.2006.08.004 |
| Journal | Nucl.Phys. A778 (2006) 10-21 |
Abstract
The sensitivity--or rather insensitivity--of the elastic proton-nucleus reaction to the neutron radius of 208Pb is investigated using a non-relativistic impulse-approximation approach. The energy region (Tlab=500 MeV and Tlab=800 MeV) is selected so that the impulse approximation may be safely assumed. Therefore, only free nucleon-nucleon scattering data are used as input for the optical potential. Further, the optical potential includes proton and neutron ground-state densities that are generated from accurately-calibrated models. Even so, these models yield a wide range of values (from 0.13 fm to 0.28 fm) for the poorly known neutron skin thickness in 208Pb. An excellent description of the experimental cross section is obtained with all neutron densities. We have invoked analytic insights developed within the eikonal approximation to understand the insensitivity of the differential cross section to the various neutron densities. As the diffractive oscillations of the cross sections are controlled by the matter radius of the nucleus, the large spread in the neutron skin among the various models gets diluted into a mere 1.5% difference in the matter radius. This renders ineffective the elastic reaction as a precision tool for the measurement of neutron radii.
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"abstract": "The sensitivity--or rather insensitivity--of the elastic proton-nucleus\nreaction to the neutron radius of 208Pb is investigated using a\nnon-relativistic impulse-approximation approach. The energy region (Tlab=500\nMeV and Tlab=800 MeV) is selected so that the impulse approximation may be\nsafely assumed. Therefore, only free nucleon-nucleon scattering data are used\nas input for the optical potential. Further, the optical potential includes\nproton and neutron ground-state densities that are generated from\naccurately-calibrated models. Even so, these models yield a wide range of\nvalues (from 0.13 fm to 0.28 fm) for the poorly known neutron skin thickness in\n208Pb. An excellent description of the experimental cross section is obtained\nwith all neutron densities. We have invoked analytic insights developed within\nthe eikonal approximation to understand the insensitivity of the differential\ncross section to the various neutron densities. As the diffractive oscillations\nof the cross sections are controlled by the matter radius of the nucleus, the\nlarge spread in the neutron skin among the various models gets diluted into a\nmere 1.5% difference in the matter radius. This renders ineffective the elastic\nreaction as a precision tool for the measurement of neutron radii.",
"arxiv_id": "nucl-th/0509019",
"authors": [
"J. Piekarewicz",
"S. P Weppner"
],
"categories": [
"nucl-th",
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],
"doi": "10.1016/j.nuclphysa.2006.08.004",
"journal_ref": "Nucl.Phys. A778 (2006) 10-21",
"title": "Insensitivity of the elastic proton-nucleus reaction to the neutron radius of 208Pb",
"url": "https://arxiv.org/abs/nucl-th/0509019"
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