65 research outputs found
Probing the isovector transition strength of the low-lying nuclear excitations induced by inverse kinematics proton scattering
A compact approach based on the folding model is suggested for the
determination of the isoscalar and isovector transition strengths of the
low-lying () excitations induced by inelastic proton
scattering measured with exotic beams. Our analysis of the recently measured
inelastic O+p scattering data at and 43 MeV/nucleon
has given for the first time an accurate estimate of the isoscalar
and isovector deformation parameters (which cannot be determined from
the (p,p') data alone by standard methods) for 2 and excited
states in O. Quite strong isovector mixing was found in the 2
inelastic O+p scattering channel, where the strength of the isovector
form factor (prototype of the Lane potential) corresponds to a
value almost 3 times larger than and a ratio of nuclear transition
matrix elements .Comment: 5 pages, 3 figure
Folding model study of the elastic scattering at low energies
The folding model analysis of the elastic scattering at the
incident energies below the reaction threshold of 34.7 MeV (in the lab system)
has been done using the well-tested density dependent versions of the M3Y
interaction and realistic choices for the He density. Because the
absorption is negligible at the energies below the reaction threshold, we were
able to probe the optical potential at low energies quite
unambiguously and found that the overlap density used to
construct the density dependence of the M3Y interaction is strongly distorted
by the Pauli blocking. This result gives possible explanation of a
long-standing inconsistency of the double-folding model in its study of the
elastic and -nucleus scattering at low energies using
the same realistic density dependent M3Y interaction
Folding model study of the charge-exchange scattering to the isobaric analog state and implication for the nuclear symmetry energy
The Fermi transition (\Delta L=\Delta S=0 and \Delta T=1) between the nuclear
isobaric analog states (IAS), induced by the charge-exchange (p,n) or (3He,t)
reaction, can be considered as "elastic" scattering of proton or 3He by the
isovector term of the optical potential (OP) that flips the projectile isospin.
The accurately measured (p,n) or (3He,t) scattering cross-section to the IAS
can be used, therefore, to probe the isospin dependence of the proton or 3He
optical potential. Within the folding model, the isovector part of the OP is
determined exclusively by the neutron-proton difference in the nuclear
densities and the isospin dependence of the effective nucleon-nucleon (NN)
interaction. Because the isovector coupling explicitly links the isovector part
of the proton or 3He optical potential to the cross section of the
charge-exchange (p,n) or (3He,t) scattering to the IAS, the isospin dependence
of the effective (in-medium) NN interaction can be well tested in the folding
model analysis of these charge-exchange reactions. On the other hand, the same
isospin- and density dependent NN interaction can also be used in a
Hartree-Fock calculation of asymmetric nuclear matter, to estimate the nuclear
matter energy and its asymmetry part (the nuclear symmetry energy). As a
result, the fine-tuning of the isospin dependence of the effective NN
interaction against the measured (p,n) or (3He,t) cross sections should allow
us to make some realistic prediction of the nuclear symmetry energy and its
density dependence.Comment: Accepted for publication in European Physical Journal A - "Hadrons
and Nuclei
Neutron star cooling - a challenge to the nuclear mean field
The two recent density-dependent versions of the finite-range M3Y interaction
(CDM3Y and M3Y-P) have been probed against the bulk properties of
asymmetric nuclear matter (NM) in the nonrelativistic Hartree Fock (HF)
formalism. The same HF study has also been done with the famous Skyrme (SLy4)
and Gogny (D1S and D1N) interactions which were well tested in the nuclear
structure calculations. Our HF results are compared with those given by other
many-body calculations like the Dirac-Brueckner Hartree-Fock approach or
ab-initio variational calculation using free nucleon-nucleon interaction, and
by both the nonrelativistic and relativistic mean-field studies using different
model parameters. Although the two considered density-dependent versions of the
M3Y interaction were proven to be quite realistic in the nuclear structure or
reaction studies, they give two distinct behaviors of the NM symmetry energy at
high densities, like the Asy-soft and Asy-stiff scenarios found earlier with
other mean-field interactions. As a consequence, we obtain two different
behaviors of the proton fraction in the -equilibrium which in turn can
imply two drastically different mechanisms for the neutron star cooling. While
some preference of the Asy-stiff scenario was found based on predictions of the
latest microscopic many-body calculations or empirical NM pressure and isospin
diffusion data deduced from heavy-ion collisions, a consistent mean-field
description of nuclear structure database is more often given by some Asy-soft
type interaction like the Gogny or M3Y-P ones. Such a dilemma poses an
interesting challenge to the modern mean-field approaches.Comment: Version accepted for publication in Phys. Rev.
Equation of state of the neutron star matter, and the nuclear symmetry energy
The nuclear mean-field potentials obtained in the Hartree-Fock method with
different choices of the in-medium nucleon-nucleon (NN) interaction have been
used to study the equation of state (EOS) of the neutron star (NS) matter. The
EOS of the uniform NS core has been calculated for the np composition in
the -equilibrium at zero temperature, using version Sly4 of the Skyrme
interaction as well as two density-dependent versions of the finite-range M3Y
interaction (CDM3Y and M3Y-P), and versions D1S and D1N of the Gogny
interaction. Although the considered effective NN interactions were proven to
be quite realistic in numerous nuclear structure and/or reaction studies, they
give quite different behaviors of the symmetry energy of nuclear matter at
supranuclear densities that lead to the \emph{soft} and \emph{stiff} scenarios
discussed recently in the literature. Different EOS's of the NS core and the
EOS of the NS crust given by the compressible liquid drop model have been used
as input of the Tolman-Oppenheimer-Volkov equations to study how the nuclear
symmetry energy affects the model prediction of different NS properties, like
the cooling process as well as the gravitational mass, radius, and moment of
inertia.Comment: To be published in Physical Review
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