81.
Dynamics of Heavy-Ion Collisions at Fermi Energies: Challenges and
Opportunities
- Schroeder, W. Udo; Toke, Jan
The dynamics of heavy-ion reactions at Fermi energies is dominated by a
dissipative mechanism modified by the concurrent emission of non-statistical
nucleons, light particles, and nuclear clusters. Experimental observables are
available to monitor the relaxation processes driving the evolution of an
interacting nuclear system towards equilibrium. Isospin degrees of freedom
provide interesting new access to fundamental information on the reaction
mechanism and the effective in-medium nucleonic interactions.
82.
Hyperon-hyperon interactions and properties of neutron matter
- Vidaña, I.; Polls, A.; Ramos, A.; Engvik, L.; Hjorth-Jensen, M.
We present results from Brueckner-Hartree-Fock calculatons for beta stable
neutron star matter with nucleonic and hyperonic degress degrees of freedom,
employing the most recent parametrizations of the baryon-baryon interaction of
the Nijmegen group. It is found that the only strange baryons emergin in beta
stable matter up to total barionic densities of 1.2 fm^-3 are $\Sigma^-$ and
$\Lambda$. The corresponding equations of state are then used to compute
properties of neutron stars such as masses and radii.
83.
Hyperon effects on the properties of $\beta$-stable neutron star matter
- Vidaña, I.; Polls, A.; Ramos, A.; Engvik, L.; Hjorth-Jensen, M.
We present results from Brueckner-Hartree-Fock calculations for
$\beta$-stable neutron star matter with nucleonic and hyperonic degrees of
freedom employing the most recent parametrizations of the baryon-baryon
interaction of the Nijmegen group. Only $\Sigma^-$ and $\Lambda$ are present up
to densities $\sim 7\rho_0$. The corresponding equations of state are then used
to compute properties of neutron stars such as masses and radii.
84.
Pairing Interaction and Self-Consistent Densities in Neutron-Rich Nuclei
- Dobaczewski, J.; Nazarewicz, W.; Reinhard, P. -G.
Particle and pairing densities in spherical even-even neutron-rich nuclei are
studied within the Skyrme-Hartree-Fock-Bogoliubov approach with the
density-dependent pairing interaction. The influence of the density dependence
of the pairing interaction on asymptotic properties of nucleonic distributions
are analyzed. It is demonstrated that the size of the neutron halo dramatically
depends on the behavior of the pairing interaction at low density.
85.
The two-nucleon system in the $\Delta$ region including full meson
retardation
- Schwamb, Michael; Arenhoevel, Hartmuth
A model is developed for the hadronic and electromagnetic interaction in the
two-nucleon system above pion threshold in the framework of meson, nucleon and
$\Delta$ degrees of freedom. It is based on time-ordered perturbation theory
and includes full meson retardation in potentials and exchange currents as well
as loop contributions to the nucleonic one-body current. Results for $NN$
scattering and deuteron photodisintegration are presented.
86.
Neutron Star Structure with Hyperons and Quarks
- Baldo, M.; Burgio, G. F.; Schulze, H. -J.
We discuss the high-density nuclear equation of state within the
Brueckner-Hartree-Fock approach. Particular attention is paid to the effects of
nucleonic three-body forces, the presence of hyperons, and the joining with an
eventual quark matter phase. The resulting properties of neutron stars, in
particular the mass-radius relation, are determined. It turns out that stars
heavier than 1.3 solar masses contain necessarily quark matter.
87.
Size Effects in Heavy Ions Fragmentation
- Barrañón, A.; López, J. A.; Dorso, C. O.
Rise-Plateau Caloric curves for different Heavy Ion collisions have been
obtained, in the range of experimental observations. Limit temperature
decreases when the residual size is increased, in agreement with recent
theoretical analysis of experimental results reported by other Collaborations.
Besides, promptly emitted particles influence on temperature plateau is shown.
LATINO binary interaction semiclassical model is used to reproduce the
inter-nucleonic forces via Pandharipande Potential and fragments are detected
with an Early Cluster Recognition Algorithm.
88.
Short-Range Correlations in Nuclear Matter at Finite Temperatures and
High Densities
- Froemel, Frank; Lenske, Horst; Mosel, Ulrich
The density and temperature dependence of nucleonic single particle spectral
function in symmetric nuclear matter at finite temperatures and densities
beyond normal nuclear matter density is investigated in a model emphasizing
short-range correlations and phase space aspects. A simple but self-consistent
approach based on quantum transport theory is used. In particular we consider
the density and temperature regime occuring e.g. during the core collapse in a
supernova explosion and the subsequent formation of a neutron star. Mean-field
effects are incorporated by a Skyrme type potential.
89.
The Relativistic Dirac-Brueckner Approach to Nuclear Matter
- Fuchs, Christian
An overview on the relativistic Dirac-Brueckner approach to the nuclear
many-body problem is given. Different approximation schemes are discussed, with
particular emphasis on the nuclear self-energy and the saturation mechanism of
nuclear matter. I will further discuss extensions of the standard approach,
amongst other things the inclusion of non-nucleonic degrees of freedom,
many-body forces and finally compare relativistic and non-relativistic
approaches.
90.
Rescaling of Nuclear Structure Functions
- Akulinichev, S. V.
It is shown that nucleonic structure functions are $x-$ and $Q^{2}-$rescaled
in nuclei. The $x-$rescaling accounts for nuclear effects in the case of exact
scaling, while the $Q^{2}-$rescaling is responsible for a corresponding
modification of quantum corrections. This result is obtained in the leading
order for all flavour combinations and connects the two known models for the
EMC-effect. Electroproduction and gluonic nuclear structure functions are
calculated.
91.
The Nuclear response in the isoscalar channel
- Cenni, R.; Conte, F.; Saracco, P.
The nuclear response is evaluated in the frame of the bosonic loop expansion
in a purely nucleonic dynamical scheme, which seems to be reliable in handling
those channels where a direct excitation of a $\Delta$-resonance is not
allowed. It is shown that the response strongly depends upon the effective
interaction in the spin-transverse isovector channel. New experiments at CEBAF
on parity-violating electron scattering could further constrain the form of the
effective interaction.
92.
Pseudoscalar meson photoproduction: from known to undiscovered resonances
- Saghai, Bijan; Tabakin, Frank
The role of dynamics in spin observables for pseudoscalar meson
photoproduction is investigated using a density matrix approach in a multipole
truncated framework. Extraction of novel rules for $\gamma p \rightarrow \pi^+
n,~ K^+ \Lambda$ and $\eta p$ reactions based on resonance dominance, and on
other broad and reasonable dynamical assumptions, are discussed. Observables
that are particularly sensitive to missing nucleonic resonances predicted by
quark-based approaches, are singled out.
93.
Antiproton Production in p+d Reaction at Subthreshold Energies
- Hasegawa, A.; Iwasaki, Y.; Sakamoto, K.; Noda, N.; Kouno, H.; Nakano, M.
An enhancement of antiprotons produced in p+d reaction in comparison with
ones in p+p elementary reaction is investigated.
In the neighborhood of subthreshold energy the enhancement is caused by the
difference of available energies for antiproton production. The cross section
in p+d reaction, on the other hand, becomes just twice of the one in elementary
p+p reaction at the incident energy far from the threshold energy when
non-nucleonic components in deuteron target are not considered.
94.
On nuclear transport at small excitations
- Hofmann, H.; Ivanyuk, F. A.
Numerical computations of transport coefficients at low temperatures are
presented for shapes typically encountered in nuclear fission. The influence of
quantum effects of the nucleonic degrees of freedom is examined, with pair
correlations included. Consequences for global collective motion are studied
for the case of the decay rate. The range of temperatures is specified above
which this motion may be described as a quantal diffusion process.
95.
Quaiselastic scattering from relativistic bound nucleons:
Transverse-Longitudinal response
- Udias, J. M.; Caballero, J. A.; de Guerra, E. Moya; Amaro, J. E.; Donnelly, T. W.
Predictions for electron induced proton knockout from the $p_{1/2}$ and
$p_{3/2}$ shells in $^{16}$O are presented using various approximations for the
relativistic nucleonic current. Results for the differential cross section,
transverse-longitudinal response ($R_{TL}$) and left-right asymmetry $A_{TL}$
are compared at $|Q^2|=0.8$ (GeV/c)$^2$ corresponding to TJNAF experiment
89-003. We show that there are important dynamical and kinematical relativistic
effects which can be tested by experiment.
96.
Constrained Orthogonal Polynomials
- Giraud, B. G.
We define sets of orthogonal polynomials satisfying the additional constraint
of a vanishing average. These are of interest, for example, for the study of
the Hohenberg-Kohn functional for electronic or nucleonic densities and for the
study of density fluctuations in centrifuges. We give explicit properties of
such polynomial sets, generalizing Laguerre and Legendre polynomials. The
nature of the dimension 1 subspace completing such sets is described. A
numerical example illustrates the use of such polynomials.
97.
QMC calculations of symmetric nuclear matter
- Gandolfi, S.; Pederiva, F.; Fantoni, S.; Schmidt, K. E.
We present an accurate numerical study of the equation of state of nuclear
matter based on realistic nucleon--nucleon interactions by means of Auxiliary
Field Diffusion Monte Carlo (AFDMC) calculations. The AFDMC method samples the
spin and isospin degrees of freedom allowing for quantum simulations of large
nucleonic systems and represents an important step forward towards a
quantitative understanding of problems in nuclear structure and astrophysics.
98.
Shell Structure of Exotic Nuclei
- Dobaczewski, J.; Michel, N.; Nazarewicz, W.; Ploszajczak, M.; Rotureau, J.
Theoretical predictions and experimental discoveries for neutron-rich,
short-lived nuclei far from stability indicate that the familiar concept of
nucleonic shell structure should be considered as less robust than previously
thought. The notion of single-particle motion in exotic nuclei is reviewed with
a particular focus on three aspects: (i) variations of nuclear mean field with
neutron excess due to tensor interactions; (ii) importance of many-body
correlations; and (iii) influence of open channels on properties of weakly
bound and unbound nuclear states.
99.
Protoneutron stars within the Brueckner-Bethe-Goldstone theory
- Nicotra, O. E.; Baldo, M.; Burgio, G. F.; Schulze, H. -J.
We study the structure of newly born neutron stars (protoneutron stars)
within the finite temperature Brueckner-Bethe-Goldstone theoretical approach
including also hyperons. We find that for purely nucleonic stars both finite
temperature and neutrino trapping reduce the value of the maximum mass. For
hyperonic stars the effect is reversed, because neutrino trapping shifts the
appearance of hyperons to larger baryon density and stiffens considerably the
equation of state.
100.
Nuclear Transport at Low Excitations
Numerical computations of transport coefficients at low temperatures are presented for shapes typically encountered in nuclear fission. The influence of quantum effects of the nucleonic degrees of freedom is examined, with pair correlations included. Consequences for global collective motion are studied for the case of the decay rate. The range of temperatures is specified above which this motion may be described as a quantal diffusion process.
