576 research outputs found
Study of nuclear correlation effects via 12C(p,n)12N(g.s.,1+) at 296 MeV
We report measurements of the cross section and a complete set of
polarization observables for the Gamow--Teller reaction at a bombarding
energy of 296 MeV.
The data are compared with distorted wave impulse approximation calculations
employing transition form factors normalized to reproduce the observed
beta-decay value.
The cross section is significantly under-predicted by the calculations at
momentum transfers 0.5 .
The discrepancy is partly resolved by considering the non-locality of the
nuclear mean field. However, the calculations still under-predict the cross
section at large momentum transfers of 1.6 .
We also performed calculations employing random phase approximation response
functions and found that the observed enhancement can be attributed in part to
pionic correlations in nuclei.Comment: 5 figures, submitted to Phys. Lett.
Complete set of polarization transfer coefficients for the reaction at 346 MeV and 0 degrees
We report measurements of the cross-section and a complete set of
polarization transfer coefficients for the reaction at a
bombarding energy = 346 MeV and a reaction angle =
.
The data are compared with the corresponding free nucleon-nucleon values on
the basis of the predominance of quasi-elastic scattering processes.
Significant discrepancies have been observed in the polarization transfer
, which are presumably the result of the three-proton =
3/2 resonance.
The spin--parity of the resonance is estimated to be , and the
distribution is consistent with previous results obtained for the same reaction
at = 48.8 MeV.Comment: 4 figures, Accepted for publication in Physical Review
Thin Ice Target for O(p,p') experiment
A windowless and self-supporting ice target is described. An ice sheet with a
thickness of 29.7 mg/cm cooled by liquid nitrogen was placed at the target
position of a magnetic spectrometer and worked stably in the O
experiment at MeV. Background-free spectra were obtained.Comment: 14 pages, 4 figures, Nucl. Instr. & Meth. A (in press
Performance of the neutron polarimeter NPOL3 for high resolution measurements
We describe the neutron polarimeter NPOL3 for the measurement of polarization
transfer observables with a typical high resolution of 300 keV
at 200 MeV.
The NPOL3 system consists of three planes of neutron detectors.
The first two planes for neutron polarization analysis are made of 20 sets of
one-dimensional position-sensitive plastic scintillation counters with a size
of 100 cm 10 cm 5 cm, and they cover the area of 100
100 .
The last plane for detecting doubly scattered neutrons or recoiled protons is
made of the two-dimensional position-sensitive liquid scintillation counter
with a size of 100 cm 100 cm 10 cm.
The effective analyzing powers and double scattering
efficiencies were measured by using the three kinds
of polarized neutrons from the , , and reactions at = 198 MeV.
The performance of NPOL3 defined as
are similar to that of the
Indiana Neutron POLarimeter (INPOL) by taking into account for the counter
configuration difference between these two neutron polarimeters.Comment: 28 pages, 18 figures, submitted to Nucl. Instrum. Methods Phys. Res.
Isovector effective NN interaction in 28Si(p,n)28P(6-) at 198 MeV
We report measurements of the cross section and a complete set of polarization observables for the View the MathML source reaction at a bombarding energy of 198 MeV. The data are compared with distorted wave impulse approximation calculations employing response functions normalized to inelastic electron scattering. The spin-longitudinal polarized cross section IDq is slightly over-predicted by the calculations, while the normal spin-transverse polarized cross section IDn is significantly under-predicted. The calculated in-plane spin-transverse IDp and spin-scalar ID0 polarized cross sections agree well with the experimental data. These results are consistent with those for View the MathML source scattering at the same energy, and thus it is concluded that isospin-mixing effects are not responsible for the discrepancy between theory and experiment in the View the MathML source case. Energy half-off-shell effects as medium effects on the effective nucleon?nucleon interaction are also investigated and found to be too small to be responsible for the discrepancy
Hard-core Yukawa model for two-dimensional charge stabilized colloids
The hyper-netted chain (HNC) and Percus-Yevick (PY) approximations are used
to study the phase diagram of a simple hard-core Yukawa model of
charge-stabilized colloidal particles in a two-dimensional system. We calculate
the static structure factor and the pair distribution function over a wide
range of parameters. Using the statics correlation functions we present an
estimate for the liquid-solid phase diagram for the wide range of the
parameters.Comment: 7 pages, 9figure
Theory of asymmetric non-additive binary hard-sphere mixtures
We show that the formal procedure of integrating out the degrees of freedom
of the small spheres in a binary hard-sphere mixture works equally well for
non-additive as it does for additive mixtures. For highly asymmetric mixtures
(small size ratios) the resulting effective Hamiltonian of the one-component
fluid of big spheres, which consists of an infinite number of many-body
interactions, should be accurately approximated by truncating after the term
describing the effective pair interaction. Using a density functional treatment
developed originally for additive hard-sphere mixtures we determine the zero,
one, and two-body contribution to the effective Hamiltonian. We demonstrate
that even small degrees of positive or negative non-additivity have significant
effect on the shape of the depletion potential. The second virial coefficient
, corresponding to the effective pair interaction between two big spheres,
is found to be a sensitive measure of the effects of non-additivity. The
variation of with the density of the small spheres shows significantly
different behavior for additive, slightly positive and slightly negative
non-additive mixtures. We discuss the possible repercussions of these results
for the phase behavior of binary hard-sphere mixtures and suggest that
measurements of might provide a means of determining the degree of
non-additivity in real colloidal mixtures
Anomalous Spin Dynamics observed by High Frequency ESR in Honeycomb Lattice Antiferromagnet InCu2/3V1/3O3
High-frequency ESR results on the S=1/2 Heisenberg hexagonal antiferromagnet
InCu2/3V1/3O3 are reported. This compound appears to be a rare model substance
for the honeycomb lattice antiferromagnet with very weak interlayer couplings.
The high-temperature magnetic susceptibility can be interpreted by the S=1/2
honeycomb lattice antiferromagnet, and it shows a magnetic-order-like anomaly
at TN=38 K. Although, the resonance field of our high-frequency ESR shows the
typical behavior of the antiferromagnetic resonance, the linewidth of our
high-frequency ESR continues to increase below TN, while it tends to decrease
as the temperature in a conventional three-dimensional antiferromagnet
decreases. In general, a honeycomb lattice antiferromagnet is expected to show
a simple antiferromagnetic order similar to that of a square lattice
antiferromagnet theoretically because both antiferromagnets are bipartite
lattices. However, we suggest that the observed anomalous spin dynamics below
TN is the peculiar feature of the honeycomb lattice antiferromagnet that is not
observed in the square lattice antiferromagnet.Comment: 5 pages, 5 figure
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