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Title: Density dependent hadronic models and the relation between neutron stars and neutron skin thickness

Abstract

In the present work, we investigate the main differences in the lead neutron skin thickness, binding energy, surface energy, and density profiles obtained with two different density dependent hadron models. Our results are calculated within the Thomas-Fermi approximation with two different numerical prescriptions and compared with results obtained with a common parametrization of the nonlinear Walecka model. The neutron skin thickness is a reflex of the equation of state properties. Hence, a direct correlation is found between the neutron skin thickness and the slope of the symmetry energy. We show that within the present approximations, the asymmetry parameter for low momentum transfer polarized electron scattering is not sensitive to the model differences.

Authors:
; ; ;  [1];  [2]
  1. Depto de Fisica, CFM, Universidade Federal de Santa Catarina Florianopolis, SC, CP.476, CEP 88.040, 900 (Brazil)
  2. Centro de Fisica Teorica, Dep. de Fisica, Universidade de Coimbra, P-3004-516, Coimbra (Portugal)
Publication Date:
OSTI Identifier:
20995334
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevC.75.055805; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; APPROXIMATIONS; BINDING ENERGY; COLLECTIVE MODEL; DENSITY; ELECTRONS; EQUATIONS OF STATE; MASS NUMBER; MOMENTUM TRANSFER; NEUTRON STARS; NEUTRONS; NUCLEAR MATTER; SURFACE ENERGY; THICKNESS; THOMAS-FERMI MODEL; WALECKA MODEL

Citation Formats

Avancini, S. S., Marinelli, J. R., Menezes, D. P., Moraes, M. M. W., and Providencia, C.. Density dependent hadronic models and the relation between neutron stars and neutron skin thickness. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.055805.
Avancini, S. S., Marinelli, J. R., Menezes, D. P., Moraes, M. M. W., & Providencia, C.. Density dependent hadronic models and the relation between neutron stars and neutron skin thickness. United States. doi:10.1103/PHYSREVC.75.055805.
Avancini, S. S., Marinelli, J. R., Menezes, D. P., Moraes, M. M. W., and Providencia, C.. Tue . "Density dependent hadronic models and the relation between neutron stars and neutron skin thickness". United States. doi:10.1103/PHYSREVC.75.055805.
@article{osti_20995334,
title = {Density dependent hadronic models and the relation between neutron stars and neutron skin thickness},
author = {Avancini, S. S. and Marinelli, J. R. and Menezes, D. P. and Moraes, M. M. W. and Providencia, C.},
abstractNote = {In the present work, we investigate the main differences in the lead neutron skin thickness, binding energy, surface energy, and density profiles obtained with two different density dependent hadron models. Our results are calculated within the Thomas-Fermi approximation with two different numerical prescriptions and compared with results obtained with a common parametrization of the nonlinear Walecka model. The neutron skin thickness is a reflex of the equation of state properties. Hence, a direct correlation is found between the neutron skin thickness and the slope of the symmetry energy. We show that within the present approximations, the asymmetry parameter for low momentum transfer polarized electron scattering is not sensitive to the model differences.},
doi = {10.1103/PHYSREVC.75.055805},
journal = {Physical Review. C, Nuclear Physics},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • In the present work, we calculate the {sup 208}Pb neutron skin thickness, binding energy, surface energy, and density profiles within the Dirac solution of a density dependent hadronic model. The same calculation is performed with the NL3 parametrization of the nonlinear Walecka model. The asymmetry of a polarized electron scattered from a heavy target is also obtained within a partial wave expansion calculation. The theoretical results are then ready to be compared with the experimental results expected to be available very soon at the Thomas Jefferson National Accelerator Facility. For completeness, other nuclei such as {sup 40}Ca, {sup 48}Ca, {supmore » 66}Ni, and {sup 90}Zr are also investigated.« less
  • Density-dependent relations among the saturation properties of symmetric nuclear matter and hyperonic matter, and properties of hadron-(strange) quark stars are shown by applying the conserving nonlinear {sigma}-{omega}-{rho} hadronic mean-field theory. Nonlinear interactions are renormalized self-consistently as effective coupling constants, effective masses, and sources of equations of motion by maintaining thermodynamic consistency to the mean-field approximation. Effective masses and coupling constants at the saturation point of symmetric nuclear matter simultaneously determine the binding energy and saturation properties of hyperonic matter. The coupling constants expected from the hadronic mean-field model and SU(6) quark model for the vector coupling constants are compared bymore » calculating masses of hadron-quark neutron stars. The nonlinear {sigma}-{omega}-{rho} mean-field approximation with vacuum fluctuation corrections and strange quark matter defined by the MIT-bag model were employed to examine properties of hadron-(strange) quark stars. We found that hadron-(strange) quark stars become more stable at high densities compared to pure hadronic and strange quark stars.« less
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  • 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 asmore » 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.« less
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