5,810 research outputs found
Coulomb and nuclear effects in breakup and reaction cross sections
We use a three-body Continuum Discretized Coupled Channel (CDCC) model to
investigate Coulomb and nuclear effects in breakup and reaction cross sections.
The breakup of the projectile is simulated by a finite number of square
integrable wave functions. First we show that the scattering matrices can be
split in a nuclear term, and in a Coulomb term. This decomposition is based on
the Lippmann-Schwinger equation, and requires the scattering wave functions. We
present two different methods to separate both effects. Then, we apply this
separation to breakup and reaction cross sections of 7Li + 208Pb. For breakup,
we investigate various aspects, such as the role of the alpha + t continuum,
the angular-momentum distribution, and the balance between Coulomb and nuclear
effects. We show that there is a large ambiguity in defining the 'Coulomb' and
'nuclear' breakup cross sections, since both techniques, although providing the
same total breakup cross sections, strongly differ for the individual
components. We suggest a third method which could be efficiently used to
address convergence problems at large angular momentum. For reaction cross
sections, interference effects are smaller, and the nuclear contribution is
dominant above the Coulomb barrier. We also draw attention on different
definitions of the reaction cross section which exist in the literature, and
which may induce small, but significant, differences in the numerical values.Comment: 12 pages, 11 figure
A Semiclassical Approach to Fusion Reactions
The semiclassical method of Alder and Winther is generalized to study fusion
reactions. As an illustration, we evaluate the fusion cross section in a
schematic two-channel calculation. The results are shown to be in good
agreement with those obtained with a quantal Coupled-Channels calculation. We
suggest that in the case of coupling to continuum states this approach may
provide a simpler alternative to the Continuum Discretized Coupled-Channels
method.Comment: 6 pages, 1 figure, invited talk at the International Symposium "A new
era of Nuclear Structure Physics", Niigata, Japan, Nov. 19-22 200
A consistent four-body CDCC model of low-energy reactions: Application to 9Be + 208Pb
We investigate the Be + Pb elastic scattering, breakup and fusion
at energies around the Coulomb barrier. The three processes are described
simultaneously, with identical conditions of calculations. The Be nucleus
is defined in an + n three-body model, using the
hyperspherical coordinate method. We first analyze spectroscopic properties of
Be, and show that the model provides a fairly good description of the
low-lying states. The scattering with Pb is then studied with the
Continuum Discretized Coupled Channel (CDCC) method, where the
+ n continuum is approximated by a discrete number of pseudostates. Optical
potentials for the + Pb and n+ Pb systems are taken
from the literature. We present elastic-scattering and fusion cross sections at
different energies.Comment: 8 pages, 3 figures, Proceedings of the International Conference on
Nucleus-Nucleus Collisions, NN 2015, Catania-Italy. arXiv admin note:
substantial text overlap with arXiv:1410.641
Transverse Isotropy in Identical Particle Scattering
It is pointed out that the cross section for the scattering of identical
charged bosons is isotropic over a broad angular range around 90 degrees when
the Sommerfeld parameter has a critical value, which depends exclusively on the
spin of the particle. A discussion of systems where this phenomenon can be
observed is presented.Comment: 8 pages, RevTeX format, 2 figures (.eps format
Improved WKB approximation for quantum tunneling: Application to heavy ion fusion
In this paper we revisit the one-dimensional tunneling problem. We consider
Kemble's approximation for the transmission coefficient. We show how this
approximation can be extended to above-barrier energies by performing the
analytical continuation of the radial coordinate to the complex plane. We
investigate the validity of this approximation by comparing their predictions
for the cross section and for the barrier distribution with the corresponding
quantum mechanical results. We find that the extended Kemble's approximation
reproduces the results of quantum mechanics with great accuracy.Comment: 8 pages, 6 figures, in press, in European. Phys. Journal A (2017
Approximate transmission coefficients in heavy ion fusion
In this paper we revisit the one-dimensional tunnelling problem. We consider
different approximations for the transmission through the Coulomb barrier in
heavy ion collisions at near-barrier energies. First, we discuss approximations
of the barrier shape by functional forms where the transmission coefficient is
known analytically. Then, we consider Kemble's approximation for the
transmission coefficient. We show how this approximation can be extended to
above-barrier energies by performing the analytical continuation of the radial
coordinate to the complex plane. We investigate the validity of the different
approximations considered in this paper by comparing their predictions for
transmission coefficients and cross sections of three heavy ion systems with
the corresponding quantum mechanical results.Comment: 12 pages, 6 figure
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