666 research outputs found
Theta dependence of CP^9 model
We apply to the model two recently proposed numerical techniques for
simulation of systems with a theta term. The algorithms, successfully tested in
the strong coupling limit, are applied to the weak coupling region. The results
agree and errors have been evaluated and are at % level. The results scale well
with the renormalization group equation and show that, for in presence
of a theta term, CP symmetry is spontaneously broken at in the
continuum limit.Comment: 4 pages, 4 figure
Perfect topological charge for asymptotically free theories
The classical equations of motion of the perfect lattice action in
asymptotically free spin and gauge models possess scale invariant
instanton solutions. This property allows the definition of a topological
charge on the lattice which is perfect in the sense that no topological defects
exist. The basic construction is illustrated in the O(3) non--linear
--model and the topological susceptibility is measured to high
precision in the range of correlation lengths . Our results
strongly suggest that the topological susceptibility is not a physical quantity
in this model.Comment: Contribution to Lattice'94, 3 pages PostScript, uuencoded compresse
Light hadron spectrum and quark masses in QCD with two flavors of dynamical quarks
We present updated results of the CP-PACS calculation of the light hadron
spectrum in full QCD. Simulations are made with an RG-improved
gauge action and a tadpole-improved clover quark action for sea quark masses
corresponding to --0.6 and the lattice
spacing --0.09 fm. A comparison of the full QCD spectrum with new
quenched results, obtained with the same improved action, shows clearly the
existence of sea quark effects in vector meson masses. Results for light quark
masses in QCD are also presented.Comment: Latex 3 pages, 6 PostScript figures, Talk presented at LATTICE99(QCD
Spectrum and Quark Masses
Heavy Quarkonia from Anisotropic and Isotropic Lattices
We report on recent results for the spectrum of heavy quarkonia. Using coarse
and anisotropic lattices we achieved an unprecedented control over statistical
and systematic errors for higher excited states such as exotic hybrid states.
In a parallel study on isotropic lattices we also investigate the effect of two
dynamical flavours on the spin structure of charmonium and bottomonium for
several symmetric lattices.Comment: LATTICE'99 (heavy quarks), 3 pages, 3 figure
Eta meson mass and topology in QCD with two light flavors
We present results for the mass of the flavor singlet meson calculated on
two-flavor full QCD configurations generated by the CP-PACS full QCD project.
We also investigate topological charge fluctuations and their dependence on the
sea quark mass.Comment: LATTICE99 (QCD Spectrum and Quark Masses), LaTeX(espcrc2.sty), 3
pages, 6 eps figure
Hadron masses and decay constants in quenched QCD
We present results for the mass spectrum and decay constants using
non-perturbatively O(a) improved Wilson fermions. Three values of and
30 different quark masses are used to obtain the chiral and continuum limits.
Special emphasis will be given to the question of taking the chiral limit and
the existence of non-analytic behavior predicted by quenched chiral
perturbation theory.Comment: LATTICE99(spectrum), 3 pages, 6 figure
String Breaking in Quenched QCD
We present preliminary quenched results on a new operator for the
investigation of string-breaking within SU(2)-colour QCD. The ground-state of a
spatially-separated static-light meson-antimeson pair is a combination of a
state with two distinct mesons, expected to dominate for large separations, and
a state where the light-quarks have annihilated, which contributes for short
distances. The crossover between these two regimes provides a measure of the
string-breaking scale length.Comment: LATTICE98(confine), 3 pages, 4 figure
Heavy-light decay constants from clover heavy quark action in QCD with two flavors of dynamical quarks
We present results on an analysis of the decay constants f_B and f_Bs with
two flavours of sea quark. The calculation has been carried out on 3 different
bare gauge couplings and 4 sea quark masses at each gauge coupling, with
m_pi/m_rho ranging from 0.8 to 0.6. We employ the Fermilab formalism to perform
calculations with heavy quarks whose mass is in the range of the b-quark. A
detailed comparison with a quenched calculation using the same action is made
to elucidate the effects due to the sea quarks.Comment: Contribution to Lattice 99 (Heavy Quarks). Latex file, uses
espcrc2.sty and epsf.sty. 3 pages, 3 encapsulated postscript figure
Equation of state in finite-temperature QCD with improved Wilson quarks
We study finite-temperature phase transition and equation of state for
two-flavor QCD at using an RG-improved gauge action and a
meanfield-improved clover quark action. The pressure is computed using the
integral method. The O(4) scaling of chiral order parameter is also examined.Comment: LATTICE99(finite temperature), 3 page
Full QCD Light Hadron Spectrum and Quark Masses: Final Results from CP-PACS
We present the final results of the CP-PACS calculation of the light hadron
spectrum and quark masses with two flavors of dynamical quarks. Simulations are
made with a renormalization-group improved gauge action and a mean-field
improved clover quark action for sea quark masses corresponding to --0.6 and the lattice spacing --0.11 fm. For
the meson spectrum in the continuum limit a clearly improved agreement with
experiment is observed compared to the quenched case, demonstrating the
importance of sea quark effects. For light quark masses we obtain
MeV and
MeV (-input) and
MeV (-input), which are reduced by
about 25% compared to the values in quenched QCD.Comment: Lattice 2000 (Spectrum), 4 pages, 3 figure
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