154 research outputs found
Thermodynamic properties of QCD with two flavors of Wilson-type lattice quarks
I report on a study of finite temperature QCD by the CP-PACS Collaboration
toward a precise determination of the equation of state with dynamical u,d
quarks. Based on a systematic simulation using improved Wilson-type quarks on
lattices with temporal size and 6, the energy density and pressure are
calculated as functions of temperature and renormalized light quark mass in the
range --2.5 and --0.95. Results
for are found to contain significant scaling violations, while results
for are suggested to be not far from the continuum limit. On the other
hand, the quark mass dependence in the EOS turned out to be small for m_{\rm
PS}/m_{\rm V} \simlt 0.8.Comment: Talk presented at Statistical QCD, Aug. 26-30, 2001, Bielefeld,
Germany. LaTeX2e, 6 pages, 4 PS figures, espcrc1.sty neede
New results on cut-off effects in spectroscopy with the fixed point action
Our study on the cut-off effects in quenched light hadron spectroscopy and
pion scattering length with the fixed point action is extended by results
obtained at a lattice spacing a=0.102 fm in a box of size L=1.8 fm. The cut-off
effects are small, but clearly seen as the resolution is increased from a=0.153
fm to a=0.102 fm. In the quark mass region where the errors are small and under
control, our results on the APE plot lie close to the extrapolated numbers of
the CP-PACS Collaboration.Comment: 15 pages, 11 figures, reference correcte
Strange quark mass from Finite Energy QCD sum rules to five loops
The strange quark mass is determined from a new QCD Finite Energy Sum Rule
(FESR) optimized to reduce considerably the systematic uncertainties arising
from the hadronic resonance sector. As a result, the main uncertainty in this
determination is due to the value of . The correlator of
axial-vector divergences is used in perturbative QCD to five-loop order,
including quark and gluon condensate contributions, in the framework of both
Fixed Order (FOPT), and Contour Improved Perturbation Theory (CIPT). The latter
exhibits very good convergence, leading to a remarkably stable result in the
very wide range , where is the radius of the
integration contour in the complex energy (squared) plane. The value of the
strange quark mass in this framework at a scale of 2 GeV is for , respectively.Comment: Additional comments added at the end of the Conclusions, and one
extra reference is given. A note added in proof uses the most recent
determination of Lambda_QCD from ALEPH to narrow down the predictio
Charmed meson spectra and decay constants with one-loop improved relativistic heavy quark action
We calculate charmed meson spectra and decay constants in lattice QCD
employing one-loop improved heavy quark action and axial-vector
currents. In quenched simulations at fm with the plaquette gauge
action as well as a renormalization-group improved one, it is shown that the
deviation from the continuum dispersion relation and the violation of
space-time symmetry for the pseudoscalar meson decay constants are
substantially reduced, once the improvement is applied. Preliminary
results with two flavors of dynamical quarks are also presented.Comment: 3 pages, 4 figure, talk presented at Lattice2004(heavy), Fermilab,
June 21-26, 200
I=2 Pion Scattering Length from Two-Pion Wave Functions
We calculate the two-pion wave function in the ground state of the I=2
-wave system and find the interaction range between two pions, which allows
us to examine the validity of the necessary condition for the finite-volume
method for the scattering length proposed by L\"uscher. We work in the quenched
approximation employing a renormalization group improved gauge action for
gluons and an improved Wilson action for quarks at on
, and lattices. We conclude
that the necessary condition is satisfied within the statistical errors for the
lattice sizes () when the quark mass is in the range
that corresponds to . We obtain the
scattering length with a smaller statistical error from the wave function than
from the two-pion time correlator.Comment: LaTeX2e, 34 pages, 11 eps figures, uses revtex4 and graphic
Do we understand the unquenched value of fB?
I review our qualitative understanding of the increase in the value of the B
meson decay constant (fB), when dynamical fermions are included in lattice QCD
calculations.Comment: 4 pages. Talk at UK Phenomenology Workshop on Heavy Flavour and CP
Violation, Durham, 17 - 22 September 2000 (Minor typo fixed
A scaling study of the step scaling function of quenched QCD with improved gauge actions
We study the scaling behavior of the step scaling function for SU(3) gauge
theory, employing the Iwasaki gauge action and the Luescher-Weisz gauge action.
In particular, we test the choice of boundary counter terms and apply a
perturbative procedure for removal of lattice artifacts for the simulation
results in the extrapolation procedure. We confirm the universality of the step
scaling functions at both weak and strong coupling regions. We also measure the
low energy scale ratio with the Iwasaki action, and confirm its universality.Comment: 3 pages. Parallel talk presented at Lattice2004(improved), Fermilab,
June 21-26, 200
Non-perturbative renormalization of vector and axial vector currents in quenched QCD for a renormalization group improved gauge action
Renormalization constants of vector () and axial-vector () currents
are determined non-perturbatively in quenched QCD for an RG-improved gauge
action and a tadpole-improved clover quark action using the Schr\"odinger
functional method. Meson decay constants and show much better
scaling when and estimated for infinite physical volume are used
instead of -factors from tadpole-improved one-loop perturbation theory.Comment: Lattice2003(improve), 3 page
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