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Delineating effects of tensor force on the density dependence of nuclear symmetry energy
In this talk, we report results of our recent studies to delineate effects of
the tensor force on the density dependence of nuclear symmetry energy within
phenomenological models. The tensor force active in the isosinglet
neutron-proton interaction channel leads to appreciable depletion/population of
nucleons below/above the Fermi surface in the single-nucleon momentum
distribution in cold symmetric nuclear matter (SNM). We found that as a
consequence of the high momentum tail in SNM the kinetic part of the symmetry
energy is significantly below the well-known Fermi gas
model prediction of approximately . With about 15%
nucleons in the high momentum tail as indicated by the recent experiments at
J-Lab by the CLAS Collaboration, the is negligibly small.
It even becomes negative when more nucleons are in the high momentum tail in
SNM. These features have recently been confirmed by three independent studies
based on the state-of-the-art microscopic nuclear many-body theories. In
addition, we also estimate the second-order tensor force contribution to the
potential part of the symmetry energy. Implications of these findings in
extracting information about nuclear symmetry energy from nuclear reactions are
discussed briefly.Comment: Talk given by Chang Xu at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
Relationship between the symmetry energy and the single-nucleon potential in isospin-asymmetric nucleonic matter
In this contribution, we review the most important physics presented
originally in our recent publications. Some new analyses, insights and
perspectives are also provided. We showed recently that the symmetry energy
and its density slope at an arbitrary density
can be expressed analytically in terms of the magnitude and momentum dependence
of the single-nucleon potentials using the Hugenholtz-Van Hove (HVH) theorem.
These relationships provide new insights about the fundamental physics
governing the density dependence of nuclear symmetry energy. Using the isospin
and momentum (k) dependent MDI interaction as an example, the contribution of
different terms in the single-nucleon potential to the and
are analyzed in detail at different densities. It is shown that the
behavior of is mainly determined by the first-order symmetry
potential of the single-nucleon potential. The density
slope depends not only on the first-order symmetry potential
but also the second-order one . Both the
and at normal density are
constrained by the isospin and momentum dependent nucleon optical potential
extracted from the available nucleon-nucleus scattering data. The
especially at high density and momentum affects
significantly the , but it is theoretically poorly understood and
currently there is almost no experimental constraints known.Comment: 9 pages, 6 figures, Review paper, Contribution to the "Topical Issue"
on "Nuclear Symmetry Energy" in European Physical Journal
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