15 research outputs found
Fusion at deep subbarrier energies: potential inversion revisited
For a single potential barrier, the barrier penetrability can be inverted
based on the WKB approximation to yield the barrier thickness. We apply this
method to heavy-ion fusion reactions at energies well below the Coulomb barrier
and directly determine the inter-nucleus potential between the colliding
nuclei. To this end, we assume that fusion cross sections at deep subbarrier
energies are governed by the lowest barrier in the barrier distribution. The
inverted inter-nucleus potentials for the O +Sm and O
+Pb reactions show that they are much thicker than phenomenological
potentials. We discuss a consequence of such thick potential by fitting the
inverted potentials with the Bass function.Comment: 8 pages, 5 figures. Uses aipxfm.sty. A talk given at the FUSION08:
New Aspects of Heavy Ion Collisions Near the Coulomb Barrier, September
22-26, 2008, Chicago, US
Exact Stochastic Mean-Field dynamics
The exact evolution of a system coupled to a complex environment can be
described by a stochastic mean-field evolution of the reduced system density.
The formalism developed in Ref. [D.Lacroix, Phys. Rev. E77, 041126 (2008)] is
illustrated in the Caldeira-Leggett model where a harmonic oscillator is
coupled to a bath of harmonic oscillators. Similar exact reformulation could be
used to extend mean-field transport theories in Many-body systems and
incorporate two-body correlations beyond the mean-field one. The connection
between open quantum system and closed many-body problem is discussed.Comment: Proceedings series of Proceedings of "FUSION08: New Aspects of Heavy
Ion Collisions near the Coulomb Barrier", September 22-26, 2008, Chicago, US
Extraction of nucleus-nucleus potential and energy dissipation from dynamical mean-field theory
Nucleus-nucleus interaction potentials in heavy-ion fusion reactions are
extracted from the microscopic time-dependent Hartree-Fock theory. When the
center-of-mass energy is much higher than the Coulomb barrier energy, extracted
potentials identify with the frozen density approximation. As the
center-of-mass energy decreases to the Coulomb barrier energy, potentials
become energy dependent. This dependence indicates dynamical reorganization of
internal degrees of freedom and leads to a reduction of the "apparent" barrier.
Including this effect leads to the Coulomb barrier energy very close to
experimental one. Aspects of one-body energy dissipation extracted from the
mean-field theory are discussed.Comment: 6 pages, 5 figures. Uses aipxfm.sty. A talk given at the FUSION08:
New Aspects of Heavy Ion Collisions Near the Coulomb Barrier, September
22-26, 2008, Chicago, US
Coupled-Channels Approach for Dissipative Quantum Dynamics in Near-Barrier Collisions
A novel quantum dynamical model based on the dissipative quantum dynamics of
open quantum systems is presented. It allows the treatment of both
deep-inelastic processes and quantum tunneling (fusion) within a fully quantum
mechanical coupled-channels approach. Model calculations show the transition
from pure state (coherent) to mixed state (decoherent and dissipative) dynamics
during a near-barrier nuclear collision. Energy dissipation, due to
irreversible decay of giant-dipole excitations of the interacting nuclei,
results in hindrance of quantum tunneling.Comment: 8 pages, 4 figures, Invited talk by A. Diaz-Torres at the FUSION08
Conference, Chicago, September 22-26, 2008, To appear in AIP Conference
Proceeding
Studies of multiplicity in relativistic heavy-ion collisions
In this talk I'll review the present status of charged particle multiplicity
measurements from heavy-ion collisions. The characteristic features of
multiplicity distributions obtained in Au+Au collisions will be discussed in
terms of collision centrality and energy and compared to those of p+p
collisions. Multiplicity measurements of d+Au collisions at 200 GeV
nucleon-nucleon center-of-mass energy will also be discussed. The results will
be compared to various theoretical models and simple scaling properties of the
data will be identified.Comment: "Focus on Multiplicity" Internationsl Workshop on Particle
Multiplicity in Relativistic Heavy Ion Collisions, Bari, Italy, June 17-19,
2003, 16 pages, 15 figure
Mass Distributions Beyond TDHF
The mass distributions for giant dipole resonances in 32S and 132Sn decaying
through particle emission and for deep-inelastic collisions between 16O nuclei
have been investigated by implementing the Balian-Veneroni variational
technique based upon a three-dimensional time-dependent Hartree-Fock code with
realistic Skyrme interactions. The mass distributions obtained have been shown
to be significantly larger than the standard TDHF results.Comment: 6 pages, 2 figures, Based on talk by J. M. A. Broomfield at the
FUSION08 Conference, Chicago, September 22-26, 2008. Conference proceedings
to be published by AI
Reaction mechanisms in 24Mg+12C and 32S+24Mg
The occurence of "exotic" shapes in light N=Z alpha-like nuclei is
investigated for 24Mg+12C and 32S+24Mg. Various approaches of superdeformed and
hyperdeformed bands associated with quasimolecular resonant structures with low
spin are presented. For both reactions, exclusive data were collected with the
Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the
VIVITRON Tandem facility of Strasbourg. Specific structures with large
deformation were selectively populated in binary reactions and their associated
-decays studied. The analysis of the binary and ternary reaction
channels is discussed.Comment: 7 pages, 4 figures, Paper presented at the Fusion08 International
Conference on New Aspects of Heavy Ion Collisions Near the Coulomb Barrier,
Chicago. Proceedings to be published by AIP Conference Proceedings Illinois,
USA, September 22-26, 200
Opportunities for detailed fission studies using light charged particle reactions
Since its discovery in 1939, the nuclear fission process has provided much insight into the behavior of nuclei under many different conditions. As part of the nuclear chain reaction, the fission process has had a profound impact on modern society and it has consequently attracted much attention to the field of nuclear physics. In this talk, I will argue that the time is ripe for a resumption of studies of the fission process induced by light charged particle reactions. Although fission can be induced in heavy nuclei by several means, in some cases these methods suffer from the complication that fission can occur at several points during the decay chain thus mixing up contributions from different excitation energies. Using instead light charged particle reactions to excite the nuclei in question, the precise excitation energy from which fission takes place, can be determined. In fact, a number of such studies were carried out previously, and a first set of results on fission barrier heights, mass, energy and angular distributions were obtained. Applying detection techniques developed over the last decades will allow researchers to obtain detailed, high-quality data from which to probe and refine our present understanding of the process. Based on these observations, I suggest that substantial advances in the study of this process can be achieved by using simple light charged particle reactions