1,250 research outputs found
A model independent determination of using the global dependence of the dispersive bounds on the form factors
We propose a method to determine the CKM matrix element using the
global dependence of the dispersive bound on the form factors for decay. Since the lattice calculation of the form
factor is limited to the large regime, only the experimental data in a
limited kinematic range can be used in a conventional method. In our new method
which exploits the statistical distributions of the dispersive bound proposed
by Lellouch, we can utilize the information of the global dependence for
all kinematic range. As a feasibility study we determine by
combining the form factors from quenched lattice QCD, the dispersive bounds,
and the experimental data by CLEO. We show that the accuracy of can
be improved by our method.Comment: 12 pages, 13 figure
Charmonium spectroscopy with heavy Kogut-Susskind quarks
Charmonium spectroscopy with Kogut-Susskind valence quarks are carried out
for quenched QCD at and for two-flavor full QCD at .
Results for 1P--1S mass splitting and estimates of
are reported. Problems associated with
flavor breaking effects and finite size effects of states are discussed.Comment: 3 pages, contribution to the Lattice '94 conference, uuencoded
compressed ps-fil
Dual-camera system for high-speed imaging in particle image velocimetry
Particle image velocimetry is an important technique in experimental fluid
mechanics, for which it has been essential to use a specialized high-speed
camera. However, the high speed is at the expense of other performances of the
camera, i.e., sensitivity and image resolution. Here, we demonstrate that the
high-speed imaging is also possible with a pair of still cameras.Comment: 4 pages, accepted by Journal of Visualization (see
http://www.springerlink.com
Charmed hadron physics in quenched anisotropic lattice QCD
We investigate the anisotropic lattice with improved quark action as a
candidate of framework in which we can treat both the heavy and light quark
region in the same manner and systematically reduce the systematic
uncertainties. To examine applicability of anisotropic lattice, we calculate
the charmed meson spectrum and decay constants in quenched approximation. We
find consistent result with most advanced results on isotropic lattices.Comment: 3 pages, 1 figure, contribution to Fifth KEK Topical Conference -
Frontiers in Flavor Physics -, Tsukuba, Japan, November 20-22, 200
Sea Quark Effects on the Strong Coupling Constant
We present results showing that the strong coupling constant measured in
two-flavor full QCD with dynamical Kogut-Susskind quarks at exhibit
a 15\% increase due to sea quarks over that for quenched QCD at the scale
GeV . (talk at lattice93)Comment: 3 pages, compressed, uuencoded PostScript file(name:lat93ch.ps.Z
Heavy-Light Semileptonic Decays in Staggered Chiral Perturbation Theory
We calculate the form factors for the semileptonic decays of heavy-light
pseudoscalar mesons in partially quenched staggered chiral perturbation theory
(\schpt), working to leading order in , where is the heavy quark
mass. We take the light meson in the final state to be a pseudoscalar
corresponding to the exact chiral symmetry of staggered quarks. The treatment
assumes the validity of the standard prescription for representing the
staggered ``fourth root trick'' within \schpt by insertions of factors of 1/4
for each sea quark loop. Our calculation is based on an existing partially
quenched continuum chiral perturbation theory calculation with degenerate sea
quarks by Becirevic, Prelovsek and Zupan, which we generalize to the staggered
(and non-degenerate) case. As a by-product, we obtain the continuum partially
quenched results with non-degenerate sea quarks. We analyze the effects of
non-leading chiral terms, and find a relation among the coefficients governing
the analytic valence mass dependence at this order. Our results are useful in
analyzing lattice computations of form factors and when the
light quarks are simulated with the staggered action.Comment: 53 pages, 8 figures, v2: Minor correction to the section on finite
volume effects, and typos fixed. Version to be published in Phys. Rev.
Nucleon sigma term and strange quark content from lattice QCD with exact chiral symmetry
We calculate the nucleon sigma term in two-flavor lattice QCD utilizing the
Feynman-Hellman theorem. Both sea and valence quarks are described by the
overlap fermion formulation, which preserves exact chiral and flavor symmetries
on the lattice. We analyse the lattice data for the nucleon mass using the
analytical formulae derived from the baryon chiral perturbation theory. From
the data at valence quark mass set different from sea quark mass, we may
extract the sea quark contribution to the sigma term, which corresponds to the
strange quark content. We find that the strange quark content is much smaller
than the previous lattice calculations and phenomenological estimates.Comment: 27 page
Ferromagnetism in a Hubbard model for an atomic quantum wire: a realization of flat-band magnetism from even-membered rings
We have examined a Hubbard model on a chain of squares, which was proposed by
Yajima et al as a model of an atomic quantum wire As/Si(100), to show that the
flat-band ferromagnetism according to a kind of Mielke-Tasaki mechanism should
be realized for an appropriate band filling in such a non-frustrated lattice.
Reflecting the fact that the flat band is not a bottom one, the ferromagnetism
vanishes, rather than intensified, as the Hubbard U is increased. The exact
diagonalization method is used to show that the critical value of U is in a
realistic range. We also discussed the robustness of the magnetism against the
degradation of the flatness of the band.Comment: misleading terms and expressions are corrected, 4 pages, RevTex, 5
figures in Postscript, to be published in Phys. Rev. B (rapid communication
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