87 research outputs found
Staggered fermion matrix elements using smeared operators
We investigate the use of two kinds of staggered fermion operators, smeared
and unsmeared. The smeared operators extend over a hypercube, and tend to
have smaller perturbative corrections than the corresponding unsmeared
operators. We use these operators to calculate kaon weak matrix elements on
quenched ensembles at , 6.2 and 6.4. Extrapolating to the continuum
limit, we find . The
systematic error is dominated by the uncertainty in the matching between
lattice and continuum operators due to the truncation of perturbation theory at
one-loop. We do not include any estimate of the errors due to quenching or to
the use of degenerate and quarks. For the
electromagnetic penguin operators we find
and . We also use the ratio of unsmeared to
smeared operators to make a partially non-perturbative estimate of the
renormalization of the quark mass for staggered fermions. We find that tadpole
improved perturbation theory works well if the coupling is chosen to be
\alpha_\MSbar(q^*=1/a).Comment: 22 pages, 1 figure, uses eps
Weak matrix elements for CP violation
We present preliminary results of matrix elements of four-fermion operators
relevant to the determination of e and e'/e using staggered fermions.Comment: 3 pages, 4 figures, Lattice 2001 (Hadronic Matrix Elements
Kaon B parameter from quenched Lattice QCD
We present results of a large-scale simulation for the Kaon B parameter
in quenched lattice QCD with the Kogut-Susskind quark action. Calculating
at 1% statistical accuracy for seven values of lattice spacing in the range
fm on lattices up to , we verify a
quadratic dependence of theoretically predicted. Strong indications
are found that, with our level of accuracy, terms
arising from our one-loop matching procedure have to be included in the
continuum extrapolation. We present (NDR, 2 GeV)=0.628(42) as our final
value, as obtained by a fit including the term.Comment: 8 pages, Latex(revtex, epsf), 2 epsf figure
Matrix elements relevant for Delta I=1/2 rule and epsilon-prime from Lattice QCD with staggered fermions
We perform a study of matrix elements relevant for the Delta I=1/2 rule and
the direct CP-violation parameter epsilon-prime from first principles by
computer simulation in Lattice QCD. We use staggered (Kogut-Susskind) fermions,
and employ the chiral perturbation theory method for studying K to 2 Pi decays.
Having obtained a reasonable statistical accuracy, we observe an enhancement of
the Delta I=1/2 amplitude, consistent with experiment within our large
systematic errors. Finite volume and quenching effects have been studied and
were found small compared to noise. The estimates of epsilon-prime are hindered
by large uncertainties associated with operator matching. In this paper we
explain the simulation method, present the results and address the systematic
uncertainties.Comment: 40 pages, 17 figures, LATEX with epsf, to be submitted to Phys. Rev.
D. Minor errors are corrected, some wording and notation change
Evidence for hard chiral logarithms in quenched lattice QCD
We present the first direct evidence that quenched QCD differs from full QCD
in the chiral () limit, as predicted by chiral perturbation
theory, from our quenched lattice QCD simulations at . We
measured the spectrum of light hadrons on ,
and , using staggered quarks of masses ,
and . The pion masses showed clear evidence for logarithmic
violations of the PCAC relation , as predicted by
quenched chiral perturbation theory. The dependence on spatial lattice volume
precludes this being a finite size effect. No evidence was seen for such chiral
logarithms in the behaviour of the chiral condensate
.Comment: 10 pages, 4 figures, uuencoded compressed postscript fil
The Kaon B-parameter with the Wilson Quark Action using Chiral Ward Identities
We present a detailed description of the method and results of our
calculation of the kaon B parameter using the Wilson quark action in quenched
QCD at . The mixing problem of the four-quark
operators is solved non-perturbatively with full use of chiral Ward identities.
We find in the continuum limit, which agrees with
the value obtained with the Kogut-Susskind quark action.Comment: 10 pages, latex source-file, 10 figures as epsf-file, uses
espcrc2.sty. Talk given at International Workshop on Lattice QCD on Parallel
Computers, 10-15 Mar 1997, Tsukuba, Japa
Calculating using HYP staggered fermions
We present preliminary results for calculated using HYP
staggered fermions in the quenched approximation. We compare different choices
of quenched penguin operators.Comment: 3 pages, 4 figures, Contribution to Lattice 2004 International
Symposiu
Is strong CP invariance due to a massless up quark?
A standing mystery in the Standard Model is the unnatural smallness of the
strong CP violating phase. A massless up quark has long been proposed as one
potential solution. A lattice calculation of the constants of the chiral
Lagrangian essential for the determination of the up quark mass, 2 alpha_8 -
alpha_5, is presented. We find 2 alpha_8 - alpha_5 = 0.29 +/- 0.18, which
corresponds to m_u / m_d = 0.410 +/- 0.036. This is the first such calculation
using a physical number of dynamical light quarks, N_f = 3.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett., corrected small
normalization error in f_pi (conclusions were unaffected), improved lattice
spacing analysis, improved finite volume analysi
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