248 research outputs found
Meson-Baryon Couplings from QCD Sum Rules
Coupling constants of the pseudoscalar mesons to the octet baryons are
calculated in the QCD sum rule approach. Two-point correlation function of the
baryons are evaluated in a single meson state and the vacuum, which yields the
designated coupling. The emphasis is on the flavor SU(3) structure of the
coupling constants and reliability in extracting the coupling constants from
the two-point correlation functions. We first calculate the baryon-diagonal
couplings and study the reliability of the sum rule. The F/D ratio of the
coupling is determined in the SU(3) limit. We further formulate the
baryon-off-diagonal couplings using the projected correlation functions and the
vertex functions, so that the unwanted excited states do not contaminate the
sum rule. As an example, the (\pi - \Lambda - \Sigma) coupling constant is
calculated and the flavor SU(3) breaking effect is studied. We find that the
effect of SU(3) breaking on the (\pi - \Lambda - \Sigma) coupling constant is
small.Comment: 33 pages, REVTeX4, 6 figure
ppK- bound states from Skyrmions
The bound kaon approach to the strangeness in the Skyrme model is applied to
investigating the possibility of deeply bound states. We describe the
system as two-Skyrmion around which a kaon field fluctuates. Each
Skyrmion is rotated in the space of SU(2) collective coordinate. The rotational
motions are quantized to be projected onto the spin-singlet proton-proton
state. We derive the equation of motion for the kaon in the background field of
two Skyrmions at fixed positions. From the numerical solution of the equation
of motion, it is found that the energy of can be considerably small, and
that the distribution of shows molecular nature of the system.
For this deep binding, the Wess-Zumino-Witten term plays an important role. The
total energy of the system is estimated in the Born-Oppenheimer
approximation. The binding energy of the state is MeV.
The mean square radius of the subsystem is
fm.Comment: Oct 2007, 15 pages, 8 figures; added references, corrected typo
Spin-3/2 pentaquark in the QCD sum rule
We study and pentaquark states with in
the QCD sum rule approach. The QCD sum rule for positive parity states and that
for negative parity are independently derived. The sum rule suggests that there
exist the and the states. These states may be observed as
extremely narrow peaks since they can be much below the -wave threshold and
since the only allowed decay channels are in -wave, whose centrifugal
barriers are so large that the widths are strongly suppressed. The
state may be assigned to the observed and the state
can be a candidate for .Comment: 27 pages, 14 figure
On the Heaving Motion of Circular Peripheral Jet Ground Effect Machines
The heaving motion of peripheral jet ground effect machines with circular planform has been studied and the simple expressions of the equation of motion are formulated. The analysis is separated into two parts, i.e. the original peripheral jet configuration and the modified configuration equipped with the stability jets. In both cases, the behavior of the jets is quantitatively treated as the “underfed” and the “modified overfed” operation and after some simplification, second order nonlinear differential equations are derived as the equations of heaving motion. Those equations are still valid for a large amplitude heaving oscillation or for a large initial hover height. Furthermore, the frequency and damping characteristics of the small amplitude heaving oscillation can be predicted by the linearized equations of motion which are derived by the use of the approximation of small amplitude. The agreement between the analytical and experimental results is found to be comparatively good
The F/D Ratio and Meson-Baryon Couplings from QCD Sum Rules
Coupling constants of the pseudoscalar mesons to the octet baryons are
computed in the QCD sum rule approach. The pi-NN, eta-NN, pi-XiXi, eta-XiXi,
pi-SigmaSigma, eta-SigmaSigma as well as pi-Lambda-Sigma couplings are studied.
Determining the pertinent Dirac structure in the correlation function, we
analyze the couplings in the SU(3) limit. We find the F/D ratio to be \sim
0.6-0.8 that is consistent with the SU(6) value. We also estimate the SU(3)
breaking effect using a projected correlation function method.Comment: 4 pages, Talk given at XVI International Conference on Particles and
Nuclei (PANIC02), Osaka, Japan, Sep.30 - Oct.4, 200
Model-independent study of the QCD sum rule for the pi NN coupling constant
We reinvestigate the QCD sum rule for the pi NN coupling constant, g,
starting from the vacuum-to-pion matrix element of the correlation function of
the interpolating fields of two nucleons. We study in detail the physical
content of the correlation function without referring to the effective theory.
We consider the invariant correlation functions by splitting the correlation
function into different Dirac structures. We show that the coefficients of the
double-pole terms are proportional to g but that the coefficients of the
single-pole terms are not determined by g. In the chiral limit the single-pole
terms as well as the continuum terms are ill defined in the dispersion
integral. Therefore, the use of naive QCD sum rules obtained from the invariant
correlation functions is not justified. A possible procedure to avoid this
difficulty is discussed.Comment: 20 pages, 2 figure
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