250 research outputs found
Forging the Link between Nuclear Reactions and Nuclear Structure
A review of the recent applications of the dispersive optical model (DOM) is
presented. Emphasis is on the nonlocal implementation of the DOM that is
capable of describing ground-state properties accurately when data like the
nuclear charge density are available. The DOM, conceived by Claude Mahaux,
provides a unified description of both elastic nucleon scattering and structure
information related to single-particle properties below the Fermi energy. We
have recently introduced a nonlocal dispersive optical potential for both the
real and imaginary part. Nonlocal absorptive potentials yield equivalent
elastic differential cross sections for Ca as compared to local ones
but change the -dependent absorption profile suggesting important
consequences for the analysis of nuclear reactions. Below the Fermi energy,
nonlocality is essential for an accurate representation of particle number and
the nuclear charge density. Spectral properties implied by and
reactions are correctly described, including the energy distribution
of about 10\% high-momentum protons obtained at Jefferson Lab. The nonlocal DOM
allows a complete description of experimental data both above (up to 200 MeV)
and below the Fermi energy in Ca. It is further demonstrated that
elastic nucleon-nucleus scattering data constrain the spectral strength in the
continuum of orbits that are nominally bound in the independent-particle model.
Extension of this analysis to Ca allows a prediction of the neutron skin
of this nucleus that is larger than most predictions made so far.Comment: 15 pages, 8 figures; Conference proceedings of CNR*15 workshop,
Tokyo, October 2015 to be published in EPJ Web of Conference
Asymmetry dependence of proton correlations
A dispersive optical model analysis of p+40Ca and p+48Ca interactions has
been carried out. The real and imaginary potentials have been constrained from
fits to elastic scattering data, reaction cross sections, and level properties
of valence hole states deduced from (e,e'p) data. The surface imaginary
potential was found to be larger overall and the gap in this potential on
either side of the Fermi energy was found to be smaller for the neutron-rich
p+48Ca system. These results imply that protons with energies near the Fermi
surface experience larger correlations with increasing asymmetry.Comment: 4 pages, 5 figure
Self-consistent Green's function calculation of 16O at small missing energies
Calculations of the one-hole spectral function of 16O for small missing
energies are reviewed.
The self-consistent Green's function approach is employed together with the
Faddeev equations technique in order to study the coupling of both
particle-particle and particle-hole phonons to the single-particle motion. The
results indicate that the characteristics of hole fragmentation are related to
the low-lying states of 16O and an improvement of the description of this
spectrum, beyond the random phase approximation, is required to understand the
experimental strength distribution.
A first calculation in this direction that accounts for two-phonon states is
discussed.Comment: Proceedings of ``Nuclear Forces and the Quantum Many-Body Problem'',
INT, Oct. 4-8, 200
Pairing properties of nucleonic matter employing dressed nucleons
A survey of pairing properties of nucleonic matter is presented that includes
the off-shell propagation associated with short-range and tensor correlations.
For this purpose, the gap equation has been solved in its most general form
employing the complete energy and momentum dependence of the normal self-energy
contributions. The latter correlations include the self-consistent calculation
of the nucleon self-energy that is generated by the summation of ladder
diagrams. This treatment preserves the conservation of particle number unlike
approaches in which the self-energy is based on the Brueckner-Hartree-Fock
approximation. A huge reduction in the strength as well as temperature and
density range of - pairing is obtained for nuclear matter as
compared to the standard BCS treatment. Similar dramatic results pertain to
pairing of neutrons in neutron matter.Comment: 15 pages, 10 figure
Density and isospin asymmetry dependence of high-momentum components
We study the one-body momentum distribution at different densities in nuclear
matter, with special emphasis on its components at high momentum. Explicit
calculations for finite neutron-proton asymmetry, based on the ladder
self-consistent Green's function approach, allow us to access the isospin
dependence of momentum distributions and elucidate their role in neutron-rich
systems. Comparisons with the deuteron momentum distribution indicate that a
substantial proportion of high-momentum components are dominated by tensor
correlations. We identify the density dependence of these tensor correlations
in the momentum distributions. Further, we find that high-momentum components
are determined by the density of each sub-species and we provide a new isospin
asymmetry scaling of these components. We use different realistic
nucleon-nucleon interactions to quantify the model dependence of our results.Comment: 14 pages, 7 figures, 1 table. Accepted version in Phys. Rev.
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