175 research outputs found
Light quark masses from unquenched lattice QCD
We calculate the light meson spectrum and the light quark masses by lattice
QCD simulation, treating all light quarks dynamically and employing the Iwasaki
gluon action and the nonperturbatively O(a)-improved Wilson quark action. The
calculations are made at the squared lattice spacings at an equal distance
a^2~0.005, 0.01 and 0.015 fm^2, and the continuum limit is taken assuming an
O(a^2) discretization error. The light meson spectrum is consistent with
experiment. The up, down and strange quark masses in the \bar{MS} scheme at 2
GeV are \bar{m}=(m_{u}+m_{d})/2=3.55^{+0.65}_{-0.28} MeV and
m_s=90.1^{+17.2}_{-6.1} MeV where the error includes statistical and all
systematic errors added in quadrature. These values contain the previous
estimates obtained with the dynamical u and d quarks within the error.Comment: 4 pages, 3 figures, revtex4; v2: contents partly modified, published
versio
Physical Point Simulation in 2+1 Flavor Lattice QCD
We present the results of the physical point simulation in 2+1 flavor lattice
QCD with the nonperturbatively -improved Wilson quark action and the
Iwasaki gauge action at on a
lattice. The physical quark masses together with the lattice
spacing is determined with , and as physical inputs.
There are two key algorithmic ingredients to make possible the direct
simulation at the physical point: One is the mass-preconditioned
domain-decomposed HMC algorithm to reduce the computational cost. The other is
the reweighting technique to adjust the hopping parameters exactly to the
physical point. The physics results include the hadron spectrum, the quark
masses and the pseudoscalar meson decay constants. The renormalization factors
are nonperturbatively evaluated with the Schr{\"o}dinger functional method. The
results are compared with the previous ones obtained by the chiral
extrapolation method.Comment: 20 pages, 17 figures, version to appear in Phys. Rev.
Light hadron spectrum in three-flavor QCD with O(a)-improved Wilson quark action
We report on a calculation of the light hadron spectrum and quark masses in
three-flavor dynamical QCD using the non-perturbatively O(a)-improved Wilson
quark action and a renormalization-group improved gauge action. Simulations are
carried out on a 16^3 \times 32 lattice at \beta=1.9, where a^{-1} \simeq 2GeV,
with 6 ud quark masses corresponding to m_{pi}/m_{rho} \simeq 0.64-0.77 and 2 s
quark masses close to the physical value. We observe that the inclusion of
dynamical strange quark brings the lattice QCD meson spectrum to good agreement
with experiment. Dynamical strange quarks also lead to a reduction of the uds
quark masses by about 15%.Comment: 3 pages, 4 figures, Lattice2003(spectrum), Fig.1 correcte
Differential decay rate for semileptonic decays
We present our study on semileptonic decay form factors
with NRQCD action for heavy quark from a quenched lattice QCD simulation at
=5.9 on a lattice. We obtain form factors defined in the
context of heavy quark effective theory by Burdman et al. and find that their
correction is small. The limit of physical heavy and light quark masses
can be performed without introducing any model function, and we obtain a
prediction for the differential decay rate . We also discuss the
soft pion limit of the form factors.Comment: Lattice 2000, 4 pages, 4 figures, Late
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