574 research outputs found
Dynamical coupled-channel study of K* K*bar and omega phi states in a chiral quark model
A dynamical coupled-channel study of K* K*bar state with isospin 0 and omega
phi state is performed within both the chiral SU(3) quark model and the
extended chiral SU(3) quark model by solving a resonating group method (RGM)
equation. The model parameters are taken from our previous work, which gave a
satisfactory description of the energies of the octet and decuplet baryon
ground states, the binding energy of the deuteron, the nucleon-nucleon (NN)
scattering phase shifts, and the hyperon-nucleon (YN) cross sections. The
results show that the interactions of K* K*bar states are attractive, which
consequently result in K* K*bar bound states with the binding energies of about
10-70 MeV, and contrarily, no omega phi bound state is obtained. The channel
coupling effect of K* K*bar and omega phi is found to be considerably large,
which makes the binding of K* K*bar 5-45 MeV deeper. The plausible
interpretation of f_0(1710) and X(1812) being K* K*bar dominated states is
briefly discussed.Comment: 7 pages, 4 figure
Kaon-nucleon interaction in the extended chiral SU(3) quark model
The chiral SU(3) quark model is extended to include the coupling between the
quark and vector chiral fields. The one-gluon exchange (OGE) which dominantly
governs the short-range quark-quark interaction in the original chiral SU(3)
quark model is now nearly replaced by the vector-meson exchange. Using this
model, the isospin I=0 and I=1 kaon-nucleon S, P, D, F wave phase shifts are
dynamically studied by solving the resonating group method (RGM) equation.
Similar to those given by the original chiral SU(3) quark model, the calculated
results for many partial waves are consistent with the experiment, while there
is no improvement in this new approach for the P_{13} and D_{15} channels, of
which the theoretical phase shifts are too much repulsive and attractive
respectively when the laboratory momentum of the kaon meson is greater than 300
MeV.Comment: 19 pages, 16 figures. Accepted by Phys. Rev.
N K and Delta K states in the chiral SU(3) quark model
The isospin I=0 and I=1 kaon-nucleon , , , wave phase shifts are
studied in the chiral SU(3) quark model by solving the resonating group method
(RGM) equation. The calculated phase shifts for different partial waves are in
agreement with the experimental data. Furthermore, the structures of the
states with L=0, I=1 and I=2 are investigated. We find that the
interaction between and in the case of L=0, I=1 is attractive,
which is not like the situation of the system, where the -wave
interactions between and for both I=0 and I=1 are repulsive. Our
numerical results also show that when the model parameters are taken to be the
same as in our previous and scattering calculations, the
state with L=0 and I=1 is a weakly bound state with about 2 MeV binding energy,
while the one with I=2 is unbound in the present one-channel calculation.Comment: 14 pages, 6 figures. PRC70,064004(2004
Heat transfer and Fourier's law in off-equilibrium systems
We study the most suitable procedure to measure the effective temperature in
off-equilibrium systems. We analyze the stationary current established between
an off-equilibrium system and a thermometer and the necessary conditions for
that current to vanish. We find that the thermometer must have a short
characteristic time-scale compared to the typical decorrelation time of the
glassy system to correctly measure the effective temperature. This general
conclusion is confirmed analyzing an ensemble of harmonic oscillators with
Monte Carlo dynamics as an illustrative example of a solvable model of a glass.
We also find that the current defined allows to extend Fourier's law to the
off-equilibrium regime by consistently defining effective transport
coefficients. Our results for the oscillator model explain why thermal
conductivities between thermalized and frozen degrees of freedom in structural
glasses are extremely small.Comment: 7 pages, REVTeX, 4 eps figure
Sigma_c Dbar and Lambda_c Dbar states in a chiral quark model
The S-wave Sigma_c Dbar and Lambda_c Dbar states with isospin I=1/2 and spin
S=1/2 are dynamically investigated within the framework of a chiral constituent
quark model by solving a resonating group method (RGM) equation. The results
show that the interaction between Sigma_c and Dbar is attractive, which
consequently results in a Sigma_c Dbar bound state with the binding energy of
about 5-42 MeV, unlike the case of Lambda_c Dbar state, which has a repulsive
interaction and thus is unbound. The channel coupling effect of Sigma_c Dbar
and Lambda_c Dbar is found to be negligible due to the fact that the gap
between the Sigma_c Dbar and Lambda_c Dbar thresholds is relatively large and
the Sigma_c Dbar and Lambda_c Dbar transition interaction is weak.Comment: 7 pages,2 figures. arXiv admin note: text overlap with
arXiv:nucl-th/0606056 by other author
Ab initio many-body calculations of nucleon scattering on 4He, 7Li, 7Be, 12C and 16O
We combine a recently developed ab initio many-body approach capable of
describing simultaneously both bound and scattering states, the ab initio
NCSM/RGM, with an importance truncation scheme for the cluster eigenstate basis
and demostrate its applicability to nuclei with mass numbers as high as 17.
Using soft similarity renormalization group evolved chiral nucleon-nucleon
interactions, we first calculate nucleon-4He phase shifts, cross sections and
analyzing power. Next, we investigate nucleon scattering on 7Li, 7Be, 12C and
16O in coupled-channel NCSM/RGM calculations that include low-lying excited
states of these nuclei. We check the convergence of phase shifts with the basis
size and study A=8, 13, and 17 bound and unbound states. Our calculations
predict low-lying resonances in 8Li and 8B that have not been experimentally
clearly identified yet. We are able to reproduce reasonably well the structure
of the A=13 low lying states. However, we find that A=17 states cannot be
described without an improved treatment of 16O one-particle-one-hole
excitations and alpha clustering.Comment: 18 pages, 20 figure
Ab initio many-body calculations of deuteron-4He scattering and 6Li states
We extend the ab initio no-core shell model/resonating-group method
(NCSM/RGM) to projectile-target binary-cluster states where the projectile is a
deuteron. We discuss the formalism in detail and give algebraic expressions for
the integration kernels. Using a soft similarity-renormalization-group evolved
chiral nucleon-nucleon potential, we calculate deuteron-4He scattering and
investigate 6Li bound and unbound states. Virtual three-body breakup effects
are obtained in an approximated way by including excited pseudo-states of the
deuteron in the calculation. We compare our results to experiment and to a
standard NCSM calculation for 6Li.Comment: 14 pages, 13 figure
cluster structures and Hoyle-analogue states in B
The structure of and states in B is investigated
with an orthogonality condition model (OCM) based on the
Gaussian expansion method. Full levels up to the and
states around the threshold (=11.1 MeV) are reproduced
consistently with the experimental energy levels. It is shown that the
state located around the Li+ threshold has an
cluster structure, whereas the and
states have a shell-model-like compact structure. We found that
the state does not possess an -condensate-like nature
similar to the state of C (Hoyle state) which has a dilute
-condensate structure described by a configuration
with about \% probability, although the monopole transition strength of the
former is as large as that of the latter. We discuss the reasons why the
state does not have the condensate character. On the other hand,
the state just below the Li+ threshold has a
cluster structure which can be interpreted as a parity-doublet partner of the
state. We indicate that the -MeV state
() just above the threshold observed in
the Li(Li,B) reaction etc. is of the
dilute-cluster-gas-like, and is a strong candidate for the Hoyle-analogue state
which has a configuration of with about \%
probability from the analyses of the single-cluster motions in B. The
structure property of the resonant state is analyzed with the complex
scaling method.Comment: 22 pages, 9 figure
H-Dihyperon in Quark Cluster Model
The H dihyperon (DH) is studied in the framework of the SU(3) chiral quark
model. It is shown that except the chiral field, the overall effect of
the other SU(3) chiral fields is destructive in forming a stable DH. The
resultant mass of DH in a three coupled channel calculation is ranged from 2225
to 2234 .Comment: 9 pages, emte
Crystalline Bi4Ge3O12 fibers fabricated by micro-pulling down technique for optical high voltage sensing
AbstractCommonly optical high voltage sensors employ the Pockels effect in a bulk electro-optic crystal such as Bi4Ge3O12 (BGO). Typically, the maximum crystal length is 100-200mm and determined by the limits of the conventional growth technique (Czochralski). In this paper we report on the growth by a micro-pulling down technique of long single crystalline BGO fibers as an alternative to bulk crystals and their characterization for voltage sensing. The fiber thickness may range from a few 100μm to a few mm. The parameters needed for stable growth over the entire length of the crystal were analyzed and optimized. Thin rods with a length of up to 850mm were grown. Samples were characterized with respect to homogeneity of growth, residual birefringence (BGO is free of natural birefringence), crystal orientation, and performance under voltage
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