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Title: Density dependence of the symmetry energy and the equation of state of isospin asymmetric nuclear matter

Abstract

The density dependence of the symmetry energy in the equation of state of isospin asymmetric nuclear matter is studied using the isoscaling of the fragment yields and the antisymmetrized molecular dynamic calculation. It is observed that the experimental data at low densities are consistent with the form of symmetry energy, E{sub sym}{approx_equal}31.6({rho}/{rho}{sub circle}){sup 0.69}, in close agreement with those predicted by the results of variational many-body calculation. A comparison of the present result with those reported recently using the NSCL-MSU data suggests that the heavy ion studies favor a dependence of the form, E{sub sym}{approx_equal}31.6({rho}/{rho}{sub circle}){sup {gamma}}, where {gamma}=0.6-1.05. This constrains the form of the density dependence of the symmetry energy at higher densities, ruling out an extremely 'stiff' and 'soft' dependences.

Authors:
; ;  [1]
  1. Cyclotron Institute, Texas A and M University, College Station, Texas 77843 (United States)
Publication Date:
OSTI Identifier:
20995134
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 75; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevC.75.034602; (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; ASYMMETRY; COMPARATIVE EVALUATIONS; DENSITY; EQUATIONS OF STATE; HEAVY IONS; ISOSPIN; MANY-BODY PROBLEM; MOLECULAR DYNAMICS METHOD; NUCLEAR MATTER; SYMMETRY; VARIATIONAL METHODS

Citation Formats

Shetty, D. V., Yennello, S. J., and Souliotis, G. A. Density dependence of the symmetry energy and the equation of state of isospin asymmetric nuclear matter. United States: N. p., 2007. Web. doi:10.1103/PHYSREVC.75.034602.
Shetty, D. V., Yennello, S. J., & Souliotis, G. A. Density dependence of the symmetry energy and the equation of state of isospin asymmetric nuclear matter. United States. doi:10.1103/PHYSREVC.75.034602.
Shetty, D. V., Yennello, S. J., and Souliotis, G. A. Thu . "Density dependence of the symmetry energy and the equation of state of isospin asymmetric nuclear matter". United States. doi:10.1103/PHYSREVC.75.034602.
@article{osti_20995134,
title = {Density dependence of the symmetry energy and the equation of state of isospin asymmetric nuclear matter},
author = {Shetty, D. V. and Yennello, S. J. and Souliotis, G. A.},
abstractNote = {The density dependence of the symmetry energy in the equation of state of isospin asymmetric nuclear matter is studied using the isoscaling of the fragment yields and the antisymmetrized molecular dynamic calculation. It is observed that the experimental data at low densities are consistent with the form of symmetry energy, E{sub sym}{approx_equal}31.6({rho}/{rho}{sub circle}){sup 0.69}, in close agreement with those predicted by the results of variational many-body calculation. A comparison of the present result with those reported recently using the NSCL-MSU data suggests that the heavy ion studies favor a dependence of the form, E{sub sym}{approx_equal}31.6({rho}/{rho}{sub circle}){sup {gamma}}, where {gamma}=0.6-1.05. This constrains the form of the density dependence of the symmetry energy at higher densities, ruling out an extremely 'stiff' and 'soft' dependences.},
doi = {10.1103/PHYSREVC.75.034602},
journal = {Physical Review. C, Nuclear Physics},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • The symmetry energy is an important quantity in the equation of state of isospin asymmetric nuclear matter. This currently unknown quantity is key to understanding the structure of systems as diverse as the neutron-rich nuclei and neutron stars. At TAMU, we have carried out studies, aimed at understanding the symmetry energy, in a variety of reactions such as, the multifragmentation of 40Ar, 40Ca + 58Fe, 58Ni and 58Ni, 58Fe + 58Ni, 58Fe reactions at 25 - 53 AMeV, and deep-inelastic reactions of 86Kr + 124,112Sn, 64,58Ni (25 AMeV), 64Ni + 64,58Ni, 112,124Sn, 232Th, 208Pb (25 AMeV) and 136Xe + 64,58Ni,more » 112,124Sn, 232Th, 197Au (20 AMeV). Here we present an overview of some of the results obtained from these studies. The results are analyzed within the framework of statistical and dynamical models, and have important implications for future experiments using beams of neutron-rich nuclei.« less
  • Properties of symmetric and asymmetric nuclear matter have been investigated in the relativistic Dirac-Brueckner-Hartree-Fock approach based on projection techniques using the Bonn A potential. The momentum, density, and isospin dependence of the optical potentials and nucleon effective masses are studied. It turns out that the isovector optical potential depends sensitively on density and momentum, but is almost insensitive to the isospin asymmetry. Furthermore, the Dirac mass m{sub D}* and the nonrelativistic mass m{sub NR}* which parametrizes the energy dependence of the single particle spectrum, are both determined from relativistic Dirac-Brueckner-Hartree-Fock calculations. The nonrelativistic mass shows a characteristic peak structure atmore » momenta slightly above the Fermi momentum k{sub F}. The relativistic Dirac mass shows a proton-neutron mass splitting of m{sub D,n}*<m{sub D,p}* in isospin asymmetric nuclear matter. However, the nonrelativistic mass has a reversed mass splitting m{sub NR,n}*>m{sub NR,p}* which is in agreement with the results from nonrelativistic calculations.« less
  • We reexamine effects of the {rho}-{omega} meson mixing mediated by nucleon polarizations on the symmetry energy in isospin-asymmetric nuclear matter. Taking into account the rearrangement term neglected in previous studies by others, we evaluate the {rho}-{omega} mixing angle in a novel way within the relativistic mean-field models with and without chiral limits. It is found that the symmetry energy is significantly softened at high densities contrary to the finding in earlier studies. As the first step of going beyond the lowest-order calculations, we also solve the Dyson equation for the {rho}-{omega} mixing. In this case, it is found that themore » symmetry energy is not only significantly softened by the {rho}-{omega}mixing at suprasaturation densities, similar to the lowest-order {rho}-{omega} mixing, but interestingly also softened at subsaturation densities. In addition, the softening of the symmetry energy at subsaturation densities can be partly suppressed by the nonlinear self-interaction of the {sigma} meson.« less
  • The density dependence of the symmetry energy in the equation of state of isospin asymmetric nuclear matter is of significant importance for studying the structure of systems as diverse as the neutron-rich nuclei and the neutron stars. A number of reactions using the dynamical and the statistical models of multifragmentation, and the experimental isoscaling observable, are studied to extract information on the density dependence of the symmetry energy. It is observed that the dynamical and the statistical model calculations give consistent results assuming the sequential decay effect in dynamical model to be small. A comparison with several other independent studiesmore » is also made to obtain important constraints on the form of the density dependence of the symmetry energy. The comparison rules out an extremely 'stiff' and 'soft' forms of the density dependence of the symmetry energy with important implications for astrophysical and nuclear physics studies.« less
  • No abstract prepared.