Origin of the neutron skin thickness of {sup 208}Pb in nuclear mean-field models

Journal Article · Mon Nov 15 04:00:00 EST 2010 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.82.054314· OSTI ID:21499172

Centelles, M; Roca-Maza, X; Vinas, X ^[1]; Warda, M ^[1]

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1. Departament d'Estructura i Constituents de la Materia and Institut de Ciencies del Cosmos, Facultat de Fisica, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona (Spain)

We study whether the neutron skin thickness {Delta}r{sub np} of {sup 208}Pb originates from the bulk or from the surface of the nucleon density distributions, according to the mean-field models of nuclear structure, and find that it depends on the stiffness of the nuclear symmetry energy. The bulk contribution to {Delta}r{sub np} arises from an extended sharp radius of neutrons, whereas the surface contribution arises from different widths of the neutron and proton surfaces. Nuclear models where the symmetry energy is stiff, as typical of relativistic models, predict a bulk contribution in {Delta}r{sub np} of {sup 208}Pb about twice as large as the surface contribution. In contrast, models with a soft symmetry energy like common nonrelativistic models predict that {Delta}r{sub np} of {sup 208}Pb is divided similarly into bulk and surface parts. Indeed, if the symmetry energy is supersoft, the surface contribution becomes dominant. We note that the linear correlation of {Delta}r{sub np} of {sup 208}Pb with the density derivative of the nuclear symmetry energy arises from the bulk part of {Delta}r{sub np}. We also note that most models predict a mixed-type (between halo and skin) neutron distribution for {sup 208}Pb. Although the halo-type limit is actually found in the models with a supersoft symmetry energy, the skin-type limit is not supported by any mean-field model. Finally, we compute parity-violating electron scattering in the conditions of the {sup 208}Pb parity radius experiment (PREX) and obtain a pocket formula for the parity-violating asymmetry in terms of the parameters that characterize the shape of the {sup 208}Pb nucleon densities.

• OSTI ID: 21499172
• Journal Information: Physical Review. C, Nuclear Physics, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 5 Vol. 82; ISSN 0556-2813; ISSN PRVCAN
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ASYMMETRY
BARYONS
CORRELATIONS
DENSITY
DIMENSIONS
DISTRIBUTION
ELECTRONS
ELEMENTARY PARTICLES
ENERGY RANGE
EVEN-EVEN NUCLEI
FERMIONS
FLEXIBILITY
HADRONS
HEAVY NUCLEI
ISOTOPES
LEAD 208
LEAD ISOTOPES
LEPTONS
MATHEMATICAL MODELS
MEAN-FIELD THEORY
MECHANICAL PROPERTIES
NEUTRONS
NUCLEAR MODELS
NUCLEAR STRUCTURE
NUCLEI
NUCLEONS
PARITY
PARTICLE PROPERTIES
PHYSICAL PROPERTIES
PROTONS
RELATIVISTIC RANGE
SCATTERING
STABLE ISOTOPES
SURFACES
SYMMETRY
TENSILE PROPERTIES
THICKNESS