265 research outputs found
Electromagnetic Corrections in Partially Quenched Chiral Perturbation Theory
We introduce photons in Partially Quenched Chiral Perturbation Theory and
calculate the resulting electromagnetic loop-corrections at NLO for the charged
meson masses and decay constants. We also present a numerical analysis to
indicate the size of the different corrections. We show that several
phenomenologically relevant quantities can be calculated consistently with
photons which couple only to the valence quarks, allowing the use of gluon
configurations produced without dynamical photons.Comment: 11 page
Dynamical fermions on anisotropic lattices
We report on our study of two-flavor full QCD on anisotropic lattices using
-improved Wilson quarks coupled with an RG-improved glue. The bare gauge
and quark anisotropies corresponding to the renormalized anisotropy
are determined as functions of and , using
the Wilson loop and the meson dispersion relation at several lattice cutoffs
and quark masses.Comment: Lattice2002(improve), 3 pages, 3 figure
Charm quark system at the physical point of 2+1 flavor lattice QCD
We investigate the charm quark system using the relativistic heavy quark
action on 2+1 flavor PACS-CS configurations previously generated on lattice. The dynamical up-down and strange quark masses are set to
the physical values by using the technique of reweighting to shift the quark
hopping parameters from the values employed in the configuration generation. At
the physical point, the lattice spacing equals GeV and the
spatial extent fm. The charm quark mass is determined by the
spin-averaged mass of the 1S charmonium state, from which we obtain m_{\rm
charm}^{\msbar}(\mu = m_{\rm charm}^{\msbar}) = 1.260(1)(6)(35) GeV, where the
errors are due to our statistics, scale determination and renormalization
factor. An additional systematic error from the heavy quark is of order
, which is estimated to be a percent
level if the factor analytic in is of order unity. Our
results for the charmed and charmed-strange meson decay constants are
MeV, MeV, again up to the heavy quark
errors of order . Combined with the CLEO
values for the leptonic decay widths, these values yield , , where the last error is on
account of the experimental uncertainty of the decay widths.Comment: 16 pages, 12 figure
Exploring QCD at small sea quark masses with improved Wilson-type quarks
We explore the region of small sea quark masses below in
two-flavor QCD using a mean-field improved clover quark action and an
RG-improved gauge action at fm on and lattices. We find that instability of the standard BiCGStab
algorithm at small quark masses can be mostly removed by the BiCGStab(DS-)
algorithm, which employs -th minimal residual polynomials with a dynamical
selection of . We also find singular spikes of in the HMC
algorithm at moderate values of . Nature of the spike is studied.
We also study finite-size effects and chiral properties of meson masses.Comment: 3 pages, 4 figures, Lattice2002(spectrum
Non-perturbative renormalization of quark mass in Nf=2+1 QCD with the Schroedinger functional scheme
We present an evaluation of the quark mass renormalization factor for Nf=2+1
QCD. The Schroedinger functional scheme is employed as the intermediate scheme
to carry out non-perturbative running from the low energy region, where
renormalization of bare mass is performed on the lattice, to deep in the high
energy perturbative region, where the conversion to the renormalization group
invariant mass or the MS-bar scheme is safely carried out. For numerical
simulations we adopted the Iwasaki gauge action and non-perturbatively improved
Wilson fermion action with the clover term. Seven renormalization scales are
used to cover from low to high energy regions and three lattice spacings to
take the continuum limit at each scale. The regularization independent step
scaling function of the quark mass for the Nf=2+1 QCD is obtained in the
continuum limit. Renormalization factors for the pseudo scalar density and the
axial vector current are also evaluated for the same action and the bare
couplings as two recent large scale Nf=2+1 simulations; previous work of the
CP-PACS/JLQCD collaboration, which covered the up-down quark mass range heavier
than MeV and that of PACS-CS collaboration for much lighter
quark masses down to MeV. The quark mass renormalization factor is
used to renormalize bare PCAC masses in these simulations.Comment: 26 pages, 17 Postscript figures. Two tables are update
Two flavors of dynamical quarks on anisotropic lattices
We report on our study of two-flavor full QCD on anisotropic lattices using
-improved Wilson quarks coupled with an RG-improved glue. The bare gauge
and quark anisotropies corresponding to the renormalized anisotropy
are determined as functions of and , which
covers the region of spatial lattice spacings --0.16 fm and
--0.9. The calibrations of the bare anisotropies are
performed with the Wilson loop and the meson dispersion relation at 4 lattice
cutoffs and 5--6 quark masses. Using the calibration results we calculate the
meson mass spectrum and the Sommer scale . We confirm that the values of
calculated for the calibration using pseudo scalar and vector meson
energy momentum dispersion relation coincide in the continuum limit within
errors. This work serves to lay ground toward studies of heavy quark systems
and thermodynamics of QCD including the extraction of the equation of state in
the continuum limit using Wilson-type quark actions.Comment: 16 pages, 23 figures, Version accepted for publication in Physical
Review
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