40 research outputs found
A High Precision Study of the QQ(bar) Potential from Wilson Loops in the Regime of String Breaking
For lattice QCD with two sea quark flavours we compute the static quark
antiquark potential V(R) in the regime where string breaking is expected. In
order to increase statistics, we make full use of the lattice information by
including all lattice vectors R to any possible lattice separation in the
infrared regime. The corresponding paths between the lattice points are
constructed by means of a generalized Bresenham algorithm as known from
computer graphics. As a results we achieve a determination of the unquenched
potential in the range .8 to 1.5 fm with hitherto unknown precision.
Furthermore, we demonstrate some error reducing methods for the evaluation of
the transition matrix element between two- and four-quark states.Comment: 6 pages, 7 figure
An Estimate of alpha_S from Bottomonium in Unquenched QCD
We estimate the strong coupling constant from the perturbative expansion of
the plaquette. The scale is set by the 2S-1S and 1P-1S splittings in
bottomonium which are computed in NRQCD on dynamical gauge configurations with
nf=2 degenerate Wilson quarks at intermediate masses. We have increased the
statistics of our spectrum calculation in order to reliably extrapolate in the
sea-quark mass. We find a value of alpha_MS(m_Z) = 0.1118(26) which is somewhat
lower than previous estimates within NRQCD.Comment: LATTICE98(heavyqk
Flavour singlet pseudoscalar masses in N_f = 2 QCD
We perform a lattice mass analysis in the flavour singlet pseudoscalar
channel on the SESAM and TXL full QCD vacuum configurations, with 2 active
flavours of dynamical Wilson fermions at beta = 5.6. At our inverse lattice
spacing, a^-1 = 2.3 GeV, we retrieve by a chiral extrapolation to the physical
light quark masses the value m_eta' = 3.7(+8)(-4) m_pi. A crude extrapolation
from (N_f = 3) phenomenology would suggest m_eta' \approx 5.1 m_pi for N_f = 2
QCD. we verify that the mass gap between the singlet state eta' and the pi
flavour triplt state is due to gauge configurations with non-trivial topology.Comment: 8 pages, 10 figure
Improving Stochastic Estimator Techniques for Disconnected Diagrams
Disconnected diagrams are expected to be sensitive to the inclusion of
dynamical fermions. We present a feasibility study for the observation of such
effects on the nucleonic matrix elements of the axial vector current, using
SESAM full QCD vacuum configurations with Wilson fermions on
lattices, at . Starting from the standard methods developed by the
Kentucky and Tsukuba groups, we investigate the improvement from various
refinements thereof.Comment: One author added. Contribution to Lattice 1997, 3 pages LaTex, to
appear in Nucl. Phys. B (Proc. Suppl.
Light Quark Physics with Dynamical Wilson Fermions
We present results for spectroscopy, quark masses and decay constants
obtained from SESAM's and TkL's large statistics simulations of QCD with two
dynamical Wilson fermions.Comment: 3 pages; to appear in the proceedings of Lat.'9
Glueballs and string breaking from full QCD
We present results on the static potential, and torelon and glueball masses
from simulations of QCD with two flavours of dynamical Wilson fermions on
and lattices at .Comment: Talk presented by Gunnar Bali at International Symposium on Lattice
Field Theories (Lattice 97), Edinburgh, July 1997, 3 pages LaTeX
(epscrc2.sty) with 4 eps figure
Light Quark Masses with Dynamical Wilson Fermions
We determine the masses of the light and the strange quarks in the
-scheme using our high-statistics lattice simulation of QCD with
dynamical Wilson fermions. For the light quark mass we find
, which is lower than in quenched
simulations. For the strange quark, in a sea of two dynamical light quarks, we
obtain .Comment: 10 pages (latex file, uses epsf-style
Decorrelating Topology with HMC
The investigation of the decorrelation efficiency of the HMC algorithm with
respect to vacuum topology is a prerequisite for trustworthy full QCD
simulations, in particular for the computation of topology sensitive
quantities. We demonstrate that for mpi/mrho ratios <= 0.69 sufficient
tunneling between the topological sectors can be achieved, for two flavours of
dynamical Wilson fermions close to the scaling region beta=5.6. Our results are
based on time series of length 5000 trajectories.Comment: change of comments: LATTICE98(confine