2,933 research outputs found
Probing the equation of state of neutron-rich matter with intermediate energy heavy-ion collisions
Nuclear reactions induced by stable and/or radioactive neutron-rich nuclei
provide the opportunity to pin down the equation of state of neutron-rich
matter, especially the density () dependence of its isospin-dependent
part, i.e., the nuclear symmetry energy . A conservative
constraint, , around the nuclear matter saturation density has
recently been obtained from the isospin diffusion data in intermediate energy
heavy-ion collisions. We review this exciting result and discuss its
consequences and implications on nuclear effective interactions, radii and
cooling mechanisms of neutron stars.Comment: 10 pages. Invited talks at (1) International Workshop on Nuclear
Multifragmentation, Nov. 28-Dec. 1, 2005, Catania, Italy and (2) XXIX
Symposium on Nuclear Physics, Jan. 3-6, 2006, Cocoyoc, Morelos, Mexic
Nuclear matter symmetry energy and the neutron skin thickness of heavy nuclei
Correlations between the thickness of the neutron skin in finite nuclei and
the nuclear matter symmetry energy are studied in the Skyrme Hartree-Fock
model. From the most recent analysis of the isospin diffusion data in heavy-ion
collisions based on an isospin- and momentum-dependent transport model with
in-medium nucleon-nucleon cross sections, a value of MeV for the
slope of the nuclear symmetry energy at saturation density is extracted, and
this imposes stringent constraints on both the parameters in the Skyrme
effective interactions and the neutron skin thickness of heavy nuclei.
Predicted thickness of the neutron skin is fm for Pb,
fm for Sn, and fm for Sn.Comment: 6 pages, 4 figures, 1 table, revised version, to appear in PR
Constraining the Skyrme effective interactions and the neutron skin thickness of nuclei using isospin diffusion data from heavy ion collisions
Recent analysis of the isospin diffusion data from heavy-ion collisions based
on an isospin- and momentum-dependent transport model with in-medium
nucleon-nucleon cross sections has led to the extraction of a value of MeV for the slope of the nuclear symmetry energy at saturation density.
This imposes stringent constraints on both the parameters in the Skyrme
effective interactions and the neutron skin thickness of heavy nuclei. Among
the 21 sets of Skyrme interactions commonly used in nuclear structure studies,
the 4 sets SIV, SV, G, and R are found to give values
that are consistent with the extracted one. Further study on the correlations
between the thickness of the neutron skin in finite nuclei and the nuclear
matter symmetry energy in the Skyrme Hartree-Fock approach leads to predicted
thickness of the neutron skin of fm for Pb, fm for Sn, and fm for Sn.Comment: 10 pages, 4 figures, 1 Table, Talk given at 1) International
Conference on Nuclear Structure Physics, Shanghai, 12-17 June, 2006; 2) 11th
China National Nuclear Structure Physics Conference, Changchun, Jilin, 13-18
July, 200
Determination of the stiffness of the nuclear symmetry energy from isospin diffusion
With an isospin- and momentum-dependent transport model, we find that the
degree of isospin diffusion in heavy ion collisions at intermediate energies is
affected by both the stiffness of the nuclear symmetry energy and the momentum
dependence of the nucleon potential. Using a momentum dependence derived from
the Gogny effective interaction, recent experimental data from NSCL/MSU on
isospin diffusion are shown to be consistent with a nuclear symmetry energy
given by at
subnormal densities. This leads to a significantly constrained value of about
-550 MeV for the isospin-dependent part of the isobaric incompressibility of
isospin asymmetric nuclear matter.Comment: 4 pages, 4 figures, 1 table, revised version, to appear in PR
Equation of state of the hot dense matter in a multi-phase transport model
Within the framework of a multi-phase transport model, we study the equation
of state and pressure anisotropy of the hot dense matter produced in central
relativistic heavy ion collisions. Both are found to depend on the
hadronization scheme and scattering cross sections used in the model.
Furthermore, only partial thermalization is achieved in the produced matter as
a result of its fast expansion
Effect of symmetry energy on two-nucleon correlation functions in heavy-ion collisions induced by neutron-rich nuclei
Using an isospin-dependent transport model, we study the effects of nuclear
symmetry energy on two-nucleon correlation functions in heavy ion collisions
induced by neutron-rich nuclei. We find that the density dependence of the
nuclear symmetry energy affects significantly the nucleon emission times in
these collisions, leading to larger values of two-nucleon correlation functions
for a symmetry energy that has a stronger density dependence. Two-nucleon
correlation functions are thus useful tools for extracting information about
the nuclear symmetry energy from heavy ion collisions.Comment: Revised version, to appear in Phys. Rev. Let
Circumstantial evidence for a soft nuclear symmetry energy at supra-saturation densities
Within an isospin- and momentum-dependent hadronic transport model it is
shown that the recent FOPI data on the ratio in central heavy-ion
collisions at SIS/GSI energies (Willy Reisdorf {\it et al.}, NPA {\bf 781}, 459
(2007)) provide circumstantial evidence suggesting a rather soft nuclear
symmetry energy \esym at compared to the
Akmal-Pandharipande-Ravenhall prediction. Some astrophysical implications and
the need for further experimental confirmations are discussed.Comment: Version to appear in Phys. Rev. Let
Transition Density and Pressure at the Inner Edge of Neutron Star Crusts
Using the nuclear symmetry energy that has been recently constrained by the
isospin diffusion data in intermediate-energy heavy ion collisions, we have
studied the transition density and pressure at the inner edge of neutron star
crusts, and they are found to be 0.040 fm
fm and 0.01 MeV/fm MeV/fm,
respectively, in both the dynamical and thermodynamical approaches. We have
also found that the widely used parabolic approximation to the equation of
state of asymmetric nuclear matter gives significantly higher values of
core-crust transition density and pressure, especially for stiff symmetry
energies. With these newly determined transition density and pressure, we have
obtained an improved relation between the mass and radius of neutron stars.Comment: 7 pages, 3 figures, proceeding of "The International Workshop on
Nuclear Dynamics in Heavy-Ion Reactions and the Symmetry Energy (IWND2009)
Partonic effects on anisotropic flows at RHIC
We report recent results from a multiphase transport (AMPT) model on the
azimuthal anisotropies of particle momentum distributions in heavy ion
collisions at the Relativistic Heavy Ion Collider. These include higher-order
anisotropic flows and their scaling, the rapidity dependence of anisotropic
flows, and the elliptic flow of charm quarks.Comment: 7 pages, 5 figures, talk given at "Hot Quarks 2004", July 18-24,
2004, Taos Valley, NM, US
Constraining properties of neutron stars with heavy-ion reactions in terrestrial laboratories
Heavy-ion reactions provide a unique means to investigate the equation of
state (EOS) of neutron-rich nuclear matter, especially the density dependence
of the nuclear symmetry energy . The latter plays an important
role in understanding many key issues in both nuclear physics and astrophysics.
Recent analyses of heavy-ion reactions have already put a stringent constraint
on the around the saturation density. This subsequently allowed
us to constrain significantly the radii and cooling mechanisms of neutron stars
as well as the possible changing rate of the gravitational constant G.Comment: 6 pages. Talk given at the Nuclear Physics in Astrophysics III,
Dresden, Germany, March 26-31, 2007. To appear in a special volume of J. of
Phys.
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