9,829 research outputs found
Fusion and breakup in the reactions of 6,7Li and 9Be
We develop a three body classical trajectory Monte Carlo (CTMC) method to
dicsuss the effect of the breakup process on heavy-ion fusion reactions induced
by weakly bound nuclei. This method follows the classical trajectories of
breakup fragments after the breakup takes place, and thus provides an
unambiguous separation between complete and incomplete fusion cross sections.
Applying this method to the fusion reaction Li + Bi, we find that
there is a significant contribution to the total complete fusion cross sections
from the process where all the breakup fragments are captured by the target
nucleus (i.e., the breakup followed by complete fusion).Comment: 4 pages, 3 eps figures. Uses espcrc1.sty. To be published in the
proceedings of the 8th international conference on clustering aspects of
nuclear structure and dynamics, November 24 - 29, 2003, Nara, Japan (Nucl.
Phys. A
Potential inversion with subbarrier fusion data revisited
We invert experimental data for heavy-ion fusion reactions at energies well
below the Coulomb barrier in order to directly determine the internucleus
potential between the colliding nuclei. In contrast to the previous
applications of the inversion formula, we explicitly take into account the
effect of channel couplings on fusion reactions, by assuming that fusion cross
sections at deep subbarrier energies are governed by the lowest barrier in the
barrier distribution. We apply this procedure to the O +Sm and
O +Pb reactions, and find that the inverted internucleus
potential are much thicker than phenomenological potentials. A relation to the
steep fall-off phenomenon of fusion cross sections recently found at deep
subbarrier energies is also discussed.Comment: 5 pages, 3 eps figure
Probing surface diffuseness of nucleus-nucleus potential with quasielastic scattering at deep sub-barrier energies
We perform a systematic study on the surface property of nucleus-nucleus
potential in heavy-ion reactions using large-angle quasielastic scattering at
energies well below the Coulomb barrier. At these energies, the quasielastic
scattering can be well described by a single-channel potential model.
Exploiting this fact, we point out that systems which involve spherical nuclei
require the diffuseness parameter of around 0.60 fm in order to fit the
experimental data, while systems with a deformed target between 0.8 fm and 1.1
fm.Comment: 6 pages, 6 figure
Mass Deformations of Super Yang-Mills Theories in D= 2+1, and Super-Membranes: A Note
Mass deformations of supersymmetric Yang-Mills theories in three spacetime
dimensions are considered. The gluons of the theories are made massive by the
inclusion of a non-local gauge and Poincare invariant mass term due to
Alexanian and Nair, while the matter fields are given standard Gaussian
mass-terms. It is shown that the dimensional reduction of such mass deformed
gauge theories defined on or produces matrix quantum
mechanics with massive spectra. In particular, all known massive matrix quantum
mechanical models obtained by the deformations of dimensional reductions of
minimal super Yang-Mills theories in diverse dimensions are shown also to arise
from the dimensional reductions of appropriate massive Yang-Mills theories in
three spacetime dimensions. Explicit formulae for the gauge theory actions are
provided.Comment: 20 Page
Geometric Transition versus Cascading Solution
We study Vafa's geometric transition and Klebanov - Strassler solution from
various points of view in M-theory. In terms of brane configurations, we show
the detailed equivalences between the two models. In some limits, both models
have an alternative realization as fourfolds in M-theory with appropriate
G-fluxes turned on. We discuss some aspects of the fourfolds including how to
see the transition and a possible extension to the non-supersymmetric case.Comment: 34 pages, LaTex, 2 figures; v2: Some comments added and references
updated. Final version to appear in JHE
PP-wave Black holes and The Matrix Model
We discuss the sizes of a black hole in the M theory pp-wave background, and
how the transverse size can be reproduced in the matrix model.Comment: 12 pages, harvmac. v2: final version to be published in JHEP, refs.
adde
M5-brane geometries, T-duality and fluxes
We describe a duality relation between configurations of M5-branes in
M-theory and type IIB theory on Taub-NUT geometries with NSNS and RR 3-form
field strength fluxes. The flux parameters are controlled by the angles between
the M5-brane and the (T)duality directions. For one M5-brane, the duality leads
to a family of supersymmetric flux configurations which interpolates between
imaginary self-dual fluxes and fluxes similar to the Polchinski-Strassler kind.
For multiple M5-branes, the IIB configurations are related to fluxes for
twisted sector fields in orbifolds. The dual M5-brane picture also provides a
geometric interpretation for several properties of flux configurations (like
the supersymmetry conditions, their contribution to tadpoles, etc), and for
many non-trivial effects in the IIB side. Among the latter, the dielectric
effect for probe D3-branes is dual to the recombination of probe M5-branes with
background ones; also, a picture of a decay channel for non-supersymmetric
fluxes is suggested.Comment: 30 pages, 3 figure
Validity of the linear coupling approximation in heavy-ion fusion reactions at sub barrier energies
The role of higher order coupling of surface vibrations to the relative
motion in heavy-ion fusion reactions at near-barrier energies is investigated.
The coupled channels equations are solved to all orders, and also in the linear
and the quadratic coupling approximations. Taking Ni + Zr
reactions as examples, it is shown that all order couplings lead to
considerably improved agreement with the experimentally measured fusion cross
sections and average angular momenta of the compound nucleus for such heavy
nearly symmetric systems. The importance of higher order coupling is also
examined for asymmetric systems like O + Cd, Sm, for
which previous calculations of the fusion cross section seemed to indicate that
the linear coupling approximation was adequate. It is shown that the shape of
the barrier distributions and the energy dependence of the average angular
momentum can change significantly when the higher order couplings are included,
even for systems where measured fusion cross sections may seem to be well
reproduced by the linear coupling approximation.Comment: Latex file, 15 pages, 6 figure
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