462 research outputs found
Discrimination of -nucleus potentials in the angular distribution of elastic scattering of hyperons from nuclei
We theoretically investigate the elastic scattering of 50-MeV
hyperons from Si and Pb in order to clarify the radial
distribution of -nucleus (optical) potentials. The angular
distributions of differential cross sections are calculated using several
potentials that can explain experimental data of the atomic X-ray
and (, ) reaction spectra simultaneously. The magnitude and
oscillation pattern of the angular distributions are understood by the use of
nearside/farside decompositions of their scattering amplitudes. It is shown
that the resultant angular distributions can considerably discriminate among
the radial distributions of the potentials that have a repulsion inside the
nuclear surface and an attraction outside the nucleus with a sizable
absorption
Production Spectra of He(, ) Reactions with Continuum Discretized Coupled Channels
We investigate theoretically production spectra of He(,
) reactions at 1.05--1.20 GeV/ in the distorted-wave impulse
approximation, using the continuum-discretized coupled-channel method. The
production cross section of a H(1/2) ground state is also
discussed.Comment: 8 pages, 4 figures; contribution to the Proceedings of the 8th
International Conference on Quarks and Nuclear Physics (QNP2018), Tsukuba,
November 13-17, 201
Repulsion and absorption of the -nucleus potential for -He in the Li(, ) reaction
We study phenomenologically inclusive spectra of the Li(, )
reaction at 1.2 GeV/ within a distorted-wave impulse approximation with the
optimal Fermi-averaging matrix. We attempt to
clarify the property of a -nucleus potential for -He by
comparing the calculated spectra with the data of the J-PARC E10 experiment.
The result shows that the repulsive and absorptive components of the
-He potential provide the ability to explain the data of the
continuum spectra in and regions; the strengths of +30 MeV and 26 MeV are favored within the
Woods-Saxon potential, consistent with analyses for heavier nuclei. Effects of
the size and potential range for -He in the neutron excess of
0.2 are also discussed.Comment: 35 pages, 11 figure
Medium effects on production in the nuclear (, ) reaction
We study theoretically medium effects on production in the (,
) reaction, using the optimal Fermi-averaging procedure which describes
the Fermi motion of a nucleon on the on-energy-shell
reaction condition in nuclei. The result shows the strong energy and angular
dependence of the in-medium cross section,which affects
significantly the shape and magnitude of the production spectrum for
hypernuclear states in the (, ) reaction on a nuclear target.The
application to the quasi-free production via the (, )
reaction on a C target is also discussed in a Fermi gas model.Comment: 18 pages, 5 figure
The Effect of Electric Field upon the Structure of Thin Films of Some Dipolar Long-chain Molecules
Behavioral Analysis of Genetically Modified Mice Indicates Essential Roles of Neurosteroidal Estrogen
Aromatase in the mouse brain is expressed only in the nerve cells of specific brain regions with a transient peak during the neonatal period when sexual behaviors become organized. The aromatase-knockout (ArKO) mouse, generated to shed light on the physiological functions of estrogen in the brain, exhibited various abnormal behaviors, concomitant with undetectable estrogen and increased androgen in the blood. To further elucidate the effects of neurosteroidal estrogens on behavioral phenotypes, we first prepared an brain-specific aromatase transgenic (bsArTG) mouse by introduction of a human aromatase transgene controlled under a ā6.5ākb upstream region of the brain-specific promoter of the mouse aromatase gene into fertilized mouse eggs, because the ā6.5ākb promoter region was previously shown to contain the minimal essential element responsible for brain-specific spatiotemporal expression. Then, an ArKO mouse expressing the human aromatase only in the brain was generated by crossing the bsArTG mouse with the ArKO mouse. The resulting mice (ArKO/bsArTG mice) nearly recovered from abnormal sexual, aggressive, and locomotive (exploratory) behaviors, in spite of having almost the same serum levels of estrogen and androgen as the adult ArKO mouse. These results suggest that estrogens locally synthesized in the specific neurons of the perinatal mouse brain directly act on the neurons and play crucial roles in the organization of neuronal networks participating in the control of sexual, aggressive, and locomotive (exploratory) behaviors
Energy dependence of -"" effective potential derived from coupled-channel Green's function
We investigate the energy dependence of a single-channel effective potential
between the and the ""-core nucleus, which can be obtained as an
-"" equivalent local potential from a coupled-channel model for
- systems. It turns out that the imaginary part of
the resultant potential near the decay threshold can well
approximate the phase space suppression factor of
decay modes. The effects on the pole position of the state in
the channel are also discussed.Comment: 4 pages, 2 figures, Proceedings of the International Conference on
Exotic Atoms and Related Topics (EXA2011), September 5-9, 2011, Wien,
Austria, to appear in Hyperfine Interaction
Production of doubly strange hypernuclei via {\Xi}- doorways in the 16O(K-, K+) reaction at 1.8 GeV/c
We examine theoretically production of doubly strange hypernuclei, 16 {\Xi}-C
and 16 {\Lambda}{\Lambda}C, in doublecharge exchange 16O(K-, K+) reactions
using a distorted-wave impulse approximation. The inclusive K+ spectrum at the
incident momentum pK- = 1.8 GeV/c and scattering angle {\theta}lab = 0^{\circ}
is estimated in a one-step mechanism, K-p \to K+{\Xi}- via {\Xi}- doorways
caused by a {\Xi}-p-{\Lambda}{\Lambda} coupling. The calculated spectrum in the
{\Xi}- bound region indicates that the integrated cross sections are on the
order of 7-12 nb/sr for significant 1- excited states with 14C(0+, 2+) \otimes
s{\Lambda}p{\Lambda} configurations in 16 {\Lambda}{\Lambda}C via the doorway
states of the spin-stretched 15N(1/2-, 3/2-) \otimes s{\Xi}- in 16 {\Xi}-C due
to a high momentum transfer q{\Xi}- \approx 400 MeV/c. The {\Xi}- admixture
probabilities of these states are on the order of 5-9%. However, populations of
the 0+ ground state with 14C(0+) \otimes s2{\Lambda} and the 2+ excited state
with 14C(2+) \otimes s2 {\Lambda} are very small. The sensitivity of the
spectrum on the {\Xi}N-{\Lambda}{\Lambda} coupling strength enables us to
extract the nature of {\Xi}N-{\Lambda}{\Lambda} dynamics in nuclei, and the
nuclear (K-, K+) reaction can extend our knowledge of the S = -2 world.Comment: 10 pages, 3 figure
Parity doublet model for baryon octets: diquark classifications and mass hierarchy based on the quark-line diagram
We construct invariant
parity doublet models within the linear realization of the chiral symmetry.
Describing baryons as the superposition of linear representations should be
useful description for transitions toward the chiral restoration. The major
problem in the construction is that there are much more chiral representations
for baryons than in the two-flavor cases. To reduce the number of possible
baryon fields, we introduce a hierarchy between representations with good or
bad diquarks (called soft and hard baryon representations, respectively). We
use and as soft to construct a chiral
invariant Lagrangian, while the representations are assumed to be
integrated out, leaving some effective interactions. The mass splitting
associated with the strange quark mass is analyzed in the first and second
order in the meson fields in representations. We
found that the chiral constraints are
far more restrictive than the constraints used in conventional
models for baryons. After extensive analyses within and
models, we found that models in the first order of do not
reproduce the mass hierarchy correctly, although the {\GO} is satisfied. In the
second order, the masses of the positive parity channels are reproduced well up
to the first radial excitations, while some problem in the mass ordering
remains in a negative parity channel. Apparently the baryon dynamics is not
well-saturated by just and representations,
as indicated by the necessity of terms higher order in
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