1,431 research outputs found
Symmetry Energy in Nuclear Surface
Interplay between the dependence of symmetry energy on density and the
variation of nucleonic densities across nuclear surface is discussed. That
interplay gives rise to the mass dependence of the symmetry coefficient in an
energy formula. Charge symmetry of the nuclear interactions allows to introduce
isoscalar and isovector densities that are approximately independent of the
magnitude of neutron-proton asymmetry.Comment: 8 pages, 4 figures, contribution to 15th Nuclear Physics Workshop
"Marie & Pierre Curie", Kazimierz, Poland, 2008; minor correction
Symmetry Energy
Examination of symmetry energy is carried out on the basis of an elementary
binding-energy formula. Constraints are obtained on the energy value at the
normal nuclear density and on the density dependence of the energy at subnormal
densities.Comment: 10 pages, 6 figures; talk given at the 3rd Argonne/MSU/INT/JINA RIA
Theory Workshop, Argonne, April 4-7, 200
Thermodynamics of Delta resonances
The thermodynamic potential of a system of pions and nucleons is computed
including the piN interactions in the P33 channel. A consistent treatment of
the width of the resonance in this channel, the Delta(1232) resonance, is
explored in detail. In the low-density limit we recover the leading term of the
virial expansion for the thermodynamic potential. An instructive diagrammatic
interpretation of the contributions to the total baryon number is presented.
Furthermore, we examine within a fireball model the consequences for the pion
spectra in heavy-ion collisions at intermediate energies, including the effect
of collective flow. A consistent treatment of the Delta width leads to a
substantial enhancement of the pion yield at low momenta.Comment: 12 pages, 3 Postscript figures, LaTeX, elsart, epsfig, minor changes,
references added, to be published in Physics Letters
Symmetry Energy from Systematic of Isobaric Analog States
Excitation energies to isobaric states, that are analogs of ground states,
are dominated by contributions from the symmetry energy. This opens up a
possibility of investigating the symmetry energy on nucleus-by-nucleus basis.
Upon correcting energies of measured nuclear levels for shell and pairing
effects, we find that the lowest energies for a given isospin rise in
proportion to the square of isospin, allowing for an interpretation of the
coefficient of proportionality in terms of a symmetry coefficient for a given
nucleus. In the (A,Z) regions where there are enough data, we demonstrate a
Z-independence of that coefficient. We further concentrate on the A-dependence
of the coefficient, in order to learn about the density dependence of symmetry
energy in uniform matter, given the changes of the density in the surface
region. In parallel to the analysis of data, we carry out an analysis of the
coefficient for nuclei calculated within the Skyrme-Hartree-Fock (SHF)
approach, with known symmetry energy for uniform matter. While the data from
isobaric analog states suggest a simple interpretation for the A-dependent
symmetry coefficient, in terms of the surface and volume symmetry coefficients,
the SHF results point to a more complicated situation within the isovector
sector than in the isoscalar, with much stronger curvature effects in the
first. We exploit the SHF results in estimating the curvature contributions to
the symmetry coefficient. That assessment is hampered by instabilities of
common Skyrme parameterizations of nuclear interactions.Comment: 6 pages, 3 figures; talk given at IX Latin American Symposium on
Nuclear Physics and Applications, July 18-22, 2011, Quito, Ecuado
Imaging of Sources in Heavy-Ion Reactions
Imaging of sources from data within the intensity interferometry is
discussed. In the two-pion case, the relative pion source function may be
determined through the Fourier transformation of the correlation function. In
the proton-proton case, the discretized source function may be fitted to the
correlation data.Comment: 12 pages, 3 postscript figures, accepted Physics Letters
Fragments in Gaussian Wave-Packet Dynamics with and without correlations
Generalization of Gaussian trial wave functions in quantum molecular dynamics
models is introduced, which allows for long-range correlations characteristic
for composite nuclear fragments. We demonstrate a significant improvement in
the description of light fragments with correlations. Utilizing either type of
Gaussian wave functions, with or without correlations, however, we find that we
cannot describe fragment formation in a dynamic situation. Composite fragments
are only produced in simulations if they are present as clusters in the
substructure of original nuclei. The difficulty is traced to the delocalization
of wave functions during emission. Composite fragments are produced abundantly
in the Gaussian molecular dynamics in the limit .Comment: 22 pages, revtex, 6 postscript figure
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