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Nucleon Effective E-Mass in Neutron-Rich Matter from the Migdal-Luttinger Jump
The well-known Migdal-Luttinger theorem states that the jump of the
single-nucleon momentum distribution at the Fermi surface is equal to the
inverse of the nucleon effective E-mass. Recent experiments studying
short-range correlations (SRC) in nuclei using electron-nucleus scatterings at
the Jefferson National Laboratory (JLAB) together with model calculations
constrained significantly the Migdal-Luttinger jump at saturation density of
nuclear matter. We show that the corresponding nucleon effective E-mass is
consequently constrained to in
symmetric nuclear matter (SNM) and the E-mass of neutrons is smaller than that
of protons in neutron-rich matter. Moreover, the average depletion of the
nucleon Fermi sea increases (decreases) approximately linearly with the isospin
asymmetry according to for protons (neutrons). These results will help improve
our knowledge about the space-time non-locality of the single-nucleon potential
in neutron-rich nucleonic matter useful in both nuclear physics and
astrophysics.Comment: Discussions added. Version accepted by PL
High Density Behaviour of Nuclear Symmetry Energy and High Energy Heavy-Ion Collisions
High energy heavy-ion collisions are proposed as a novel means to obtain
information about the high density ({\rm HD}) behaviour of nuclear symmetry
energy. Within an isospin-dependent hadronic transport model using
phenomenological equations of state ({\rm EOS}) for dense neutron-rich matter,
it is shown that the isospin asymmetry of the HD nuclear matter formed in high
energy heavy-ion collisions is determined mainly by the HD behaviour of nuclear
symmetry energy. Experimental signatures in several sensitive probes, i.e.,
to ratio, transverse collective flow and its excitation
function as well as neutron-proton differential flow, are investigated. A
precursor of the possible isospin separation instability in dense neutron-rich
matter is predicted to appear as the local minima in the excitation functions
of the transverse flow parameter for both neutrons and protons above the pion
production threshold. Because of its {\it qualitative} nature unlike other {\it
quantitative} observables, this precursor can be used as a unique signature of
the isospin dependence of the nuclear {\rm EOS}. Measurements of these
observables will provide the first terrestrial data to constrain stringently
the HD behaviour of nuclear symmetry energy and thus also the {\rm EOS} of
dense neutron-rich matter. Implications of our findings to neutron star studies
are also discussed.Comment: 25 pages + 16 figures, Nucl. Phys. A (2002) in pres
Origins and Impacts of High-Density Symmetry Energy
What is nuclear symmetry energy? Why is it important? What do we know about
it? Why is it so uncertain especially at high densities? Can the total symmetry
energy or its kinetic part be negative? What are the effects of three-body
and/or tensor force on symmetry energy? How can we probe the density dependence
of nuclear symmetry energy with terrestrial nuclear experiments? What
observables of heavy-ion reactions are sensitive to the high-density behavior
of nuclear symmetry energy? How does the symmetry energy affect properties of
neutron stars, gravitational waves and our understanding about the nature of
strong-field gravity? In this lecture, we try to answer these questions as best
as we can based on some of our recent work and/or understanding of research
done by others. This note summarizes the main points of the lecture.Comment: Invited lecture given at the Carpathian Summer School of Physics
2016, Exotic Nuclei and Nuclear Astrophysics (VI), Sinaia, Romania, June 26
to July 9, 201
Effects of Neutron-Proton Short-Range Correlation on the Equation of State of Dense Neutron-Rich Nucleonic Matter
The strongly isospin-dependent tensor force leads to short-range correlations
(SRC) between neutron-proton (deuteron-like) pairs much stronger than those
between proton-proton and neutron-neutron pairs. As a result of the short-range
correlations, the single-nucleon momentum distribution develops a high-momentum
tail above the Fermi surface. Because of the strongly isospin-dependent
short-range correlations, in neutron-rich matter a higher fraction of protons
will be depleted from its Fermi sea and populate above the Fermi surface
compared to neutrons. This isospin-dependent nucleon momentum distribution may
have effects on: (1) nucleon spectroscopic factors of rare isotopes, (2) the
equation of state especially the density dependence of nuclear symmetry energy,
(3) the coexistence of a proton-skin in momentum space and a neutron-skin in
coordinate space (i.e., protons move much faster than neutrons near the surface
of heavy nuclei). In this talk, we discuss these features and their possible
experimental manifestations. As an example, SRC effects on the nuclear symmetry
energy are discussed in detail using a modified Gogny-Hartree-Fock (GHF) energy
density functional (EDF) encapsulating the SRC-induced high momentum tail (HMT)
in the single-nucleon momentum distribution
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