1,859 research outputs found
SU(3) lattice QCD study for octet and decuplet baryon spectra
The spectra of octet and decuplet baryons are studied using SU(3) lattice QCD
at the quenched level. As an implementation to reduce the statistical
fluctuation, we employ the anisotropic lattice with improved quark
action. In relation to , we measure also the mass of the SU(3)
flavor-singlet negative-parity baryon, which is described as a three quark
state in the quenched lattice QCD, and its lowest mass is measured about 1.6
GeV. Since the experimentally observed negative-parity baryon
is much lighter than 1.6 GeV, may include a large component of
a bound state rather than the three quark state. The mass splitting
between the octet and the decuplet baryons are also discussed in terms of the
current quark mass.Comment: 8 pages, 3 figures, proceeding of "International Symposium on Hadron
and Nuclei" at Yonsei Univ., Seoul, Korea 20-22 Feb. 200
Negative-Parity Baryons in Quenched Anisotropic Lattice QCD
We study negative-parity baryon spectra in quenched anisotropic lattice QCD.
The negative-parity baryons are measured as the parity partner of the
ground-state baryons. In addition to the flavor octet and decuplet baryons, we
pay much attention to the flavor-singlet negative-parity baryon as a
three-quark state and compare it with the Lambda(1405) baryon. Numerical
results of the flavor octet and decuplet negative-parity baryon masses are
close to experimental values of lowest-lying negative-parity baryons, while the
flavor-singlet baryon is much heavier than Lambda(1405). This indicates that
the Lambda(1405) would be a multi-quark state such as the N-Kbar molecule
rather than the flavor-singlet 3 quark state.Comment: 4 pages, 4 figs. Talk given at 16th International Conference on
Particles and Nuclei (PANIC 02), Osaka, Japan, 30 Sep - 4 Oct 200
Spin 3/2 Penta-quarks in anisotropic lattice QCD
A high-precision mass measurement for the pentaquark (5Q) Theta^+ in
J^P=3/2^{\pm} channel is performed in anisotropic quenched lattice QCD using a
large number of gauge configurations as N_{conf}=1000. We employ the standard
Wilson gauge action at beta=5.75 and the O(a) improved Wilson (clover) quark
action with kappa=0.1210(0.0010)0.1240 on a 12^3 \times 96 lattice with the
renormalized anisotropy as a_s/a_t = 4. The Rarita-Schwinger formalism is
adopted for the interpolating fields. Several types of the interpolating fields
with isospin I=0 are examined such as (a) the NK^*-type, (b) the
(color-)twisted NK^*-type, (c) a diquark-type. The chiral extrapolation leads
to only massive states, i.e., m_{5Q} \simeq 2.1-2.2 GeV in J^P=3/2^- channel,
and m_{5Q} = 2.4-2.6 GeV in J^P=3/2^+ channel. The analysis with the hybrid
boundary condition(HBC) is performed to investigate whether these states are
compact 5Q resonances or not. No low-lying compact 5Q resonance states are
found below 2.1GeV.Comment: 15 pages, 6 figures, 4 table
Naked Singularity Explosion in Higher Dimensions
Motivated by the recent argument that in the TeV-scale gravity
trans-Planckian domains of spacetime as effective naked singularities would be
generated by high-energy particle (and black-hole) collisions, we investigate
the quantum particle creation by naked-singularity formation in general
dimensions. Background spacetime is simply modeled by the self-similar Vaidya
solution, describing the spherical collapse of a null dust fluid. In a generic
case the emission power is found to be proportional to the quadratic inverse of
the remaining time to a Cauchy horizon, as known in four dimensions. On the
other hand, the power is proportional to the quartic inverse for a critical
case in which the Cauchy horizon is `degenerate'. According to these results,
we argue that the backreaction of the particle creation to gravity will be
important in particle collisions, in contrast to the gravitational collapse of
massive stellar objects, since the bulk of energy is carried away by the
quantum radiation even if a quantum gravitational effect cutoff the radiation
just before the appearance of naked singularity.Comment: 19 pages, 2 figures; v2: typos fixe
REFWA: An Efficient and Fair Congestion Control Scheme for LEO Satellite Networks
科研費報告書収録論文(課題番号:17500030/研究代表者:加藤寧/インターネットと高親和性を有する次世代低軌道衛星ネットワークに関する基盤研究
Hadron Physics and Confinement Physics in Lattice QCD
We are aiming to construct Quark Hadron Physics and Confinement Physics based
on QCD. Using SU(3) lattice QCD, we are investigating the three-quark
potential at T=0 and , mass spectra of positive and negative-parity
baryons in the octet and the decuplet representations of the SU(3) flavor,
glueball properties at T=0 and . We study also Confinement Physics
using lattice QCD. In the maximally abelian (MA) gauge, the off-diagonal gluon
amplitude is strongly suppressed, and then the off-diagonal gluon phase shows
strong randomness, which leads to a large effective off-diagonal gluon mass,
. Due to the large off-diagonal gluon mass in
the MA gauge, infrared QCD is abelianized like nonabelian Higgs theories. In
the MA gauge, there appears a macroscopic network of the monopole world-line
covering the whole system. From the monopole current, we extract the dual gluon
field , and examine the longitudinal magnetic screening. We obtain 0.5 GeV in the infrared region, which indicates the dual Higgs
mechanism by monopole condensation. From infrared abelian dominance and
infrared monopole condensation, low-energy QCD in the MA gauge is described
with the dual Ginzburg-Landau (DGL) theory.Comment: Invited talk given at International Symposium on Hadrons and Nuclei,
Seoul, Korea, 20-22 Feb 200
Numerical evaluation of anisotropic fluid flow in sheared rock fractures
Water Dynamics: 4th International Workshop on Water Dynamics, Sendai, Japan, 7-8 November 200
Comparison of various lazaroid compounds for protection against ischemic liver injury
Lazaroids are a group of 21-aminosteroids that lack steroid action but have a potent cytoprotective effect by inhibiting iron-dependent lipid peroxidation. However, there have been conflicting reports on the effectiveness and potency of the various lazaroid compounds. In this study, we compared the effectiveness of three major lazaroids on warm liver ischemia in dogs using a 2-hr hepatic vascular exclusion model. The agents were given to the animals intravenously for 30 min before ischemia. The animals were divided into 5 groups: Control (n=10), no treatment; Group F (n=6), U-74006F (10 mg/kg); Group G (n=6), U-74389G (10 mg/kg); Group A1 (n=6), U-74500A (10 mg/kg); Group A2 (n=6), U-74500A (5 mg/kg). The effect of treatment was evaluated by two-week animal survival, hepatic tissue blood flow, liver function tests, blood and tissue biochemistry, and histological analyses. Animal survival in all treated groups was significantly improved compared with the control (83-100% versus 30%). Elevation of liver enzymes after reperfusion was markedly attenuated in treated groups, except for an early significant increase in Group G. Postreperfusion hepatic tissue blood flow was much higher in all treated animals (50% of the preischemic level vs. 25% in the control). Lazaroids, particularly U-74500A at 5 mg/kg (Group A2), suppressed adenine nucleotide degradation during ischemia and enhanced the resynthesis of high-energy phosphates after reperfusion. Although structural abnormalities in postreperfusion liver tissues were markedly ameliorated in all treated groups, Group A2 showed significantly less neutrophil infiltration. Liver injury from warm ischemia and reperfusion was attenuated with all lazaroid compounds, of which U-74500A at 5 mg/kg exhibited the most significant protective activity
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