6,486 research outputs found
Prof. Ikedaâs important contributions to nuclear physics
Professor Ikeda has made many fundamental contributions to nuclear physics, especially to the theory of Gamow-Teller giant resonances, to nuclear cluster physics, to hypernuclear physics, and to the physics of neutron-rich nuclei. He also has played an important role in the education of young researchers in Japan and on the contacts between theoreticians and experimentalists
Three-body model calculations for 16C nucleus
We apply a three-body model consisting of two valence neutrons and the core
nucleus C in order to investigate the ground state properties and the
electronic quadrupole transition of the C nucleus. The discretized
continuum spectrum within a large box is taken into account by using a
single-particle basis obtained from a Woods-Saxon potential. The calculated
B(E2) value from the first 2 state to the ground state shows good agreement
with the observed data with the core polarization charge which reproduces the
experimental B(E2) value for C. We also show that the present
calculation well accounts for the longitudinal momentum distribution of
C fragment from the breakup of C nucleus. We point out that the
dominant ( configuration in the ground state of C plays a
crucial role for these agreement.Comment: 5 pages, 3 figures, 3 table
A relativistic treatment of pion wave functions in the annihilation antiproton-proton -> pi^-pi^+
Quark model intrinsic wave functions of highly energetic pions in the
reaction \bar pp->\pi^-\pi^+ are subjected to a relativistic treatment. The
annihilation is described in a constituent quark model with A2 and R2
flavor-flux topology and the annihilated quark-antiquark pairs are in 3P_0 and
3S_1 states. We study the effects of pure Lorentz transformations on the
antiquark and quark spatial wave functions and their respective spinors in the
pion. The modified quark geometry of the pion has considerable impact on the
angular dependence of the annihilation mechanisms.Comment: 10 pages in revtex format, 3 figure
Li spectrum from Li fragmentation
A recently developed time dependent model for the excitation of a nucleon
from a bound state to a continuum resonant state in the system n+core is
applied to the study of the population of the low energy continuum of the
unbound Li system obtained from Li fragmentation. Comparison of
the model results to new data from the GSI laboratory suggests that the
reaction mechanism is dominated by final state effects rather than by the
sudden process, but for the population of the l=0 virtual state, in which case
the two mechanisms give almost identical results. There is also, for the first
time, a clear evidence for the population of a d resonance in
Li.Comment: 15 pages, 4 figures, 3 tables. Accepted for publication in
Nucl.Phys.
Majorana spin-flip transitions in a magnetic trap
Atoms confined in a magnetic trap can escape by making spin-flip Majorana
transitions due to a breakdown of the adiabatic approximation. Several papers
have studied this process for atoms with spin or . The present
paper calculates the escape rate for atoms with spin . This problem has
new features because the perturbation which allows atoms to escape
satisfies a selection rule and multi-step
processes contribute in leading order. When the adiabatic approximation is
satisfied the leading order terms can be summed to yield a simple expression
for the escape rate.Comment: 16page
Alpha-cluster structure and density wave in oblate nuclei
Pentagon and triangle shapes in Si-28 and C-12 are discussed in relation with
nuclear density wave. In the antisymmetrized molecular dynamics calculations,
the band in Si-28 and the band in C-12 are described by
the pentagon and triangle shapes, respectively. These negative-parity bands can
be interpreted as the parity partners of the ground bands and they
are constructed from the parity-asymmetric-intrinsic states. The pentagon and
the triangle shapes originate in 7alpha and 3alpha cluster structures,
respectively. In a mean-field picture, they are described also by the static
one-dimensional density wave at the edge of the oblate states. In analysis with
ideal alpha cluster models using Brink-Bloch cluster wave functions and that
with a simplified model, we show that the static edge density wave for the
pentagon and triangle shapes can be understood by spontaneous breaking of axial
symmetry, i.e., the instability of the oblate states with respect to the edge
density wave. The density wave is enhanced in the Z=N nuclei due to the
proton-neutron coherent density waves, while it is suppressed in Z\ne N nuclei.Comment: 23 pages, 8 figure
Large-angle scattering and quasi-elastic barrier distributions
We study in detail the barrier distributions extracted from large-angle
quasi-elastic scattering of heavy ions at energies near the Coulomb barrier.
Using a closed-form expression for scattering from a single barrier, we compare
the quasi-elastic barrier distribution with the corresponding test function for
fusion. We examine the isocentrifugal approximation in coupled-channels
calculations of quasi-elastic scattering and find that for backward angles, it
works well, justifying the concept of a barrier distribution for scattering
processes. This method offers an interesting tool for investigating unstable
nuclei. We illustrate this for the Mg + Pb reaction, where the
quadrupole collectivity of the neutron-rich Mg remains to be clarified
experimentally.Comment: 26 pages, 10 eps figure
Revised theory of the magnetic surface anisotropy of impurities in metallic mesoscopic samples
In several experiments the magnitude of the contribution of magnetic
impurities to the Kondo resistivity shows size dependence in mesoscopic
samples. It was suggested ten years ago that magnetic surface anisotropy can be
responsible for the size dependence in cases where there is strong spin-orbit
interaction in the metallic host. The anisotropy energy has the form where is the vector perpendicular to the
plane surface, is the spin of the magnetic impurity and is
inversely proportional to distance measured from the surface. It has been
realized that in the tedious calculation an unjustified approximation was
applied for the hybridizations of the host atom orbitals with the conduction
electrons which depend on the position of the host atoms. Namely, the momenta
of the electrons were replaced by the Fermi momentum . That is
reinvestigated considering the -dependence which leads to singular energy
integrals and in contrary to the previous result is oscillating like
and the distance dependence goes like in the
asymptotic region. As the anisotropy is oscillating, for integer spin the
ground state is either a singlet or a doublet depending on distance , but in
the case of the doublet there is no direct electron induced transition between
those two states at zero temperature. Furthermore, for half-integer ()
spin it is always a doublet with direct transition only in half of the cases.Comment: 10 pages, 4 figure
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