48 research outputs found
Two-Body Density Matrix for Closed s-d Shell Nuclei
The two-body density matrix for and within the
Low-order approximation of the Jastrow correlation method is considered. Closed
analytical expressions for the two-body density matrix, the center of mass and
relative local densities and momentum distributions are presented. The effects
of the short-range correlations on the two-body nuclear characteristics are
investigated.Comment: 13 pages(LaTeX), 4 figures (ps
Temperature dependence of the volume and surface contributions to the nuclear symmetry energy within the coherent density fluctuation model
The temperature dependence of the volume and surface components of the
nuclear symmetry energy (NSE) and their ratio is investigated in the framework
of the local density approximation (LDA). The results of these quantities for
finite nuclei are obtained within the coherent density fluctuation model
(CDFM). The CDFM weight function is obtained using the temperature-dependent
proton and neutron densities calculated through the HFBTHO code that solves the
nuclear Skyrme-Hartree-Fock-Bogoliubov problem by using the cylindrical
transformed deformed harmonic-oscillator basis. We present and discuss the
values of the volume and surface contributions to the NSE and their ratio
obtained for the Ni, Sn, and Pb isotopic chains around double-magic Ni,
Sn, and Pb nuclei. The results for the -dependence of the
considered quantities are compared with estimations made previously for zero
temperature showing the behavior of the NSE components and their ratio, as well
as with the available experimental data. The sensitivity of the results on
various forms of the density dependence of the symmetry energy is studied. We
confirm the existence of `kinks' of these quantities as functions of the mass
number at MeV for the double closed-shell nuclei Ni and Sn
and the lack of `kinks' for the Pb isotopes, as well as the disappearance of
these kinks as the temperature increases.Comment: 14 pages, 12 figures, 1 table, accepted for publication in Physical
Review
Nucleon momentum distribution in deuteron and other nuclei within the light-front dynamics method
The relativistic light-front dynamics (LFD) method has been shown to give a
correct description of the most recent data for the deuteron monopole and
quadrupole charge form factors obtained at the Jefferson Laboratory for elastic
electron-deuteron scattering for six values of the squared momentum transfer
between 0.66 and 1.7 (GeV/c). The good agreement with the data is in
contrast with the results of the existing non-relativistic approaches. In this
work we firstly make a complementary test of the LFD applying it to calculate
another important characteristic, the nucleon momentum distribution of
the deuteron using six invariant functions instead of two
(- and -waves) in the nonrelativistic case. The comparison with the
-scaling data shows the decisive role of the function which at
500 MeV/c exceeds all other -functions (as well as the - and
-waves) for the correct description of of the deuteron in the
high-momentum region. Comparison with other calculations using - and
-waves corresponding to various nucleon-nucleon potentials is made.
Secondly, using clear indications that the high-momentum components of
in heavier nuclei are related to those in the deuteron, we develop an approach
within the natural orbital representation to calculate in -nuclei
on the basis of the deuteron momentum distribution. As examples, in
He, C and Fe are calculated and good agreement with the
-scaling data is obtained.Comment: 16 pages, 6 figures, corrected, to appear in Phys. Rev. C in February
200
Temperature dependence of the symmetry energy and neutron skins in Ni, Sn, and Pb isotopic chains
The temperature dependence of the symmetry energy for isotopic chains of even-even Ni, Sn, and Pb nuclei is investigated in the framework of the local density approximation (LDA). The Skyrme energy density functional with two Skyrme-class effective interactions, SkM* and SLy4, is used in the calculations. The temperature-dependent proton and neutron densities are calculated through the HFBTHO code that solves the nuclear Skyrme-Hartree-Fock-Bogoliubov problem by using the cylindrical transformed deformed harmonic-oscillator basis. In addition, two other density distributions of Pb-208, namely the Fermi-type density determined within the extended Thomas-Fermi (TF) method and symmetrized-Fermi local density obtained within the rigorous density functional approach, are used. The kinetic energy densities are calculated either by the HFBTHO code or, for a comparison, by the extended TF method up to second order in temperature (with T-2 term). Alternative ways to calculate the symmetry energy coefficient within the LDA are proposed. The results for the thermal evolution of the symmetry energy coefficient in the interval T = 0-4 MeV show that its values decrease with temperature. The temperature dependence of the neutron and proton root-mean-square radii and corresponding neutron skin thickness is also investigated, showing that the effect of temperature leads mainly to a substantial increase of the neutron radii and skins, especially in the more neutron-rich nuclei, a feature that may have consequences on astrophysical processes and neutron stars
Study of He+C Elastic Scattering Using a Microscopic Optical Potential
The He+C elastic scattering data at beam energies of 3, 38.3 and
41.6 MeV/nucleon are studied utilizing the microscopic optical potentials
obtained by a double-folding procedure and also by using those inherent in the
high-energy approximation. The calculated optical potentials are based on the
neutron and proton density distributions of colliding nuclei established in an
appropriate model for He and obtained from the electron scattering form
factors for C. The depths of the real and imaginary parts of the
microscopic optical potentials are considered as fitting parameters. At low
energy the volume optical potentials reproduce sufficiently well the
experimental data. At higher energies, generally, additional surface terms
having form of a derivative of the imaginary part of the microscopic optical
potential are needed. The problem of ambiguity of adjusted optical potentials
is resolved requiring the respective volume integrals to obey the determined
dependence on the collision energy. Estimations of the Pauli blocking effects
on the optical potentials and cross sections are also given and discussed.
Conclusions on the role of the aforesaid effects and on the mechanism of the
considered processes are made.Comment: 12 pages, 9 figures, accepted for publication in Physical Review
Calculations of He+p Elastic Cross Sections Using Microscopic Optical Potential
An approach to calculate microscopic optical potential (OP) with the real
part obtained by a folding procedure and with the imaginary part inherent in
the high-energy approximation (HEA) is applied to study the He+p elastic
scattering data at energies of tens of MeV/nucleon (MeV/N). The neutron and
proton density distributions obtained in different models for He are
utilized in the calculations of the differential cross sections. The role of
the spin-orbit potential is studied. Comparison of the calculations with the
available experimental data on the elastic scattering differential cross
sections at beam energies of 15.7, 26.25, 32, 66 and 73 MeV/N is performed. The
problem of the ambiguities of the depths of each component of the optical
potential is considered by means of the imposed physical criterion related to
the known behavior of the volume integrals as functions of the incident energy.
It is shown also that the role of the surface absorption is rather important,
in particular for the lowest incident energies (e.g., 15.7 and 26.25
MeV/nucleon).Comment: 11 pages, 7 figures, accepted for publication in Physical Review