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Title: Symmetry Energy in the Equation of State of Asymmetric Nuclear Matter

Abstract

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, 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.

Authors:
; ;  [1]
  1. Cyclotron Institute, Texas A and M University, College Station, TX 77843 (United States)
Publication Date:
OSTI Identifier:
21054840
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 884; Journal Issue: 1; Conference: 6. Latin American symposium on nuclear physics and applications, Iguazu (Argentina), 3-7 Oct 2005; Other Information: DOI: 10.1063/1.2710604; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ARGON 40; ASYMMETRY; CALCIUM 40; DEEP INELASTIC HEAVY ION REACTIONS; EQUATIONS OF STATE; GOLD 197; IRON 58; ISOSPIN; KRYPTON 86; LEAD 208; NEUTRON STARS; NEUTRON-RICH ISOTOPES; NICKEL 58; NICKEL 64; NUCLEAR FRAGMENTATION; NUCLEAR MATTER; STATISTICAL MODELS; SYMMETRY; THORIUM 232; XENON 136

Citation Formats

Yennello, S. J., Shetty, D. V., and Souliotis, G. A. Symmetry Energy in the Equation of State of Asymmetric Nuclear Matter. United States: N. p., 2007. Web. doi:10.1063/1.2710604.
Yennello, S. J., Shetty, D. V., & Souliotis, G. A. Symmetry Energy in the Equation of State of Asymmetric Nuclear Matter. United States. doi:10.1063/1.2710604.
Yennello, S. J., Shetty, D. V., and Souliotis, G. A. Mon . "Symmetry Energy in the Equation of State of Asymmetric Nuclear Matter". United States. doi:10.1063/1.2710604.
@article{osti_21054840,
title = {Symmetry Energy in the Equation of State of Asymmetric Nuclear Matter},
author = {Yennello, S. J. and Shetty, D. V. and Souliotis, G. A.},
abstractNote = {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, 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.},
doi = {10.1063/1.2710604},
journal = {AIP Conference Proceedings},
number = 1,
volume = 884,
place = {United States},
year = {Mon Feb 12 00:00:00 EST 2007},
month = {Mon Feb 12 00:00:00 EST 2007}
}
  • 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. Thismore » constrains the form of the density dependence of the symmetry energy at higher densities, ruling out an extremely 'stiff' and 'soft' dependences.« less
  • The nuclear mean-field potentials obtained in the Hartree-Fock method with different choices of the in-medium nucleon-nucleon (NN) interaction have been used to study the equation of state (EOS) of the neutron star (NS) matter. The EOS of the uniform NS core has been calculated for the npe{mu} composition in the {beta} equilibrium at zero temperature, using version Sly4 of the Skyrme interaction as well as two density-dependent versions of the finite-range M3Y interaction (CDM3Yn and M3Y-Pn), and versions D1S and D1N of the Gogny interaction. Although the considered effective NN interactions were proven to be quite realistic in numerous nuclearmore » structure and/or reaction studies, they give quite different behaviors of the symmetry energy of nuclear matter at supranuclear densities that lead to the soft and stiff scenarios discussed recently in the literature. Different EOS's of the NS core and the EOS of the NS crust given by the compressible liquid drop model have been used as input of the Tolman-Oppenheimer-Volkov equations to study how the nuclear symmetry energy affects the model prediction of different NS properties, like the cooling process as well as the gravitational mass, radius, and moment of inertia.« less
  • We present microscopic calculations of light and medium mass nuclei and the equation of state of symmetric and asymmetric nuclear matter using different nucleon-nucleon interactions, including a new Argonne version that has the same spin-isospin structure as local chiral forces at next-to-next-to-leading order. The calculations are performed using auxiliary field diffusion Monte Carlo (AFDMC) combined with an improved variational wave function and sampling technique. The AFDMC method can now be used to successfully calculate the energies of very light to medium mass nuclei as well as the energy of isospin-asymmetric nuclear matter, demonstrating microscopically the quadratic dependence of the energymore » on the symmetry energy.« less
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  • Relativistic Dirac-Brueckner calculations, based on a one-boson-exchange interaction, are presented for the equation of state of asymmetric nuclear matter. For decreasing values of the ratio Z/A it is shown that the saturation shifts to lower densities and the compression modulus at saturation drops. however, at high densities for all values of Z/A a stiff equation of state is observed, in contrast to the outcome of supernova calculations. The possibility of the occurrence of a ..pi../sup -/ condensate is discussed.