222 research outputs found
Term and Quark Spin Content of the Nucleon
We report results of our calculation on the term and quark spin
content of the nucleon on the quenched lattice at . The disconnected insertions which involve contributions from the sea
quarks are calculated with the stochastic noise algorithm. As a physical
test of the algorithm, we show that the forward matrix elements of the vector
and pseudoscalar currents for the disconnected insertions are indeed consistent
with the known results of zero. We tried the Wuppertal smeared source and found
it to be more noisy than the point source. With unrenormalized
MeV, we find the term to be MeV. The
strange quark condensate in the nucleon is large, i.e. . For the quark spin content, we find
, , and . The flavor-singlet axial charge .Comment: contribution to Lattice '94; 3 page uuencoded ps fil
Weak Decays of Heavy-Light Mesons on the Lattice: Semi-Leptonic Formfactors
We report results (on an intermediate statistics sample) of a study of weak
semi-leptonic formfactors of and decays, addressing the uncertainties
from mass extrapolations to chiral and to heavy quarks. Moreover, we present a
nonperturbative test to the LMK current renormalization scheme for vector
current {\it transition} matrix elements and find remarkable agreement.Comment: 13 pages, uuencoded, updated table
Heavy-light baryonic mass splittings from the lattice
We present lattice estimates of the mass of the heavy-light baryons
and obtained using propagating heavy quarks. For
our result is GeV, after
extrapolation to the continuum limit and in the quenched approximation.Comment: 3 pages postscript, Contribution to Lattice'9
Many Masses on One Stroke: Economic Computation of Quark Propagators
The computational effort in the calculation of Wilson fermion quark
propagators in Lattice Quantum Chromodynamics can be considerably reduced by
exploiting the Wilson fermion matrix structure in inversion algorithms based on
the non-symmetric Lanczos process. We consider two such methods: QMR (quasi
minimal residual) and BCG (biconjugate gradients). Based on the decomposition
of the Wilson mass matrix, using QMR, one can carry
out inversions on a {\em whole} trajectory of masses simultaneously, merely at
the computational expense of a single propagator computation. In other words,
one has to compute the propagator corresponding to the lightest mass only,
while all the heavier masses are given for free, at the price of extra storage.
Moreover, the symmetry can be used to cut
the computational effort in QMR and BCG by a factor of two. We show that both
methods then become---in the critical regime of small quark
masses---competitive to BiCGStab and significantly better than the standard MR
method, with optimal relaxation factor, and CG as applied to the normal
equations.Comment: 17 pages, uuencoded compressed postscrip
Dynamical Quark Effects in QCD
We discuss latest results of lattice QCD simulations with dynamical fermions.
Special emphasis is paid to the subjects of the static quark potential, the
light hadron spectrum, spectrum, and the pion-nucleon-sigma term.Comment: 6 pages, 9 figures, invited talk at LAT9
Determining gA using non-perturbatively O(a) improved Wilson fermions
A completely non-perturbative estimate is given for gA using both quenched
and unquenched O(a) improved Wilson fermions. Particular attention is paid to
the determination of the axial renormalisation constant, ZA, using the Ward
identity for the propagator. For the quenched case, we have results at three
lattice spacings allowing a continuum extrapolation.Comment: Lattice 2000 (Hadronic Matrix Elements), 4 page
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