871 research outputs found
Numerical Tests of the Improved Fermilab Action
Recently, the Fermilab heavy-quark action was extended to include
dimension-six and -seven operators in order to reduce the discretization
errors. In this talk, we present results of the first numerical simulations
with this action (the OK action), where we study the masses of the quarkonium
and heavy-light systems. We calculate combinations of masses designed to test
improvement and compare results obtained with the OK action to their
counterparts obtained with the clover action. Our preliminary results show a
clear improvement.Comment: 7 pages, 3 figures, Talk presented at 28th International Symposium On
Lattice Field Theory (Lattice 2010) 13-19 Jun 2010, Villasimius, Sardinia,
Ital
Application of heavy-quark effective theory to lattice QCD: III. Radiative corrections to heavy-heavy currents
We apply heavy-quark effective theory (HQET) to separate long- and
short-distance effects of heavy quarks in lattice gauge theory. In this paper
we focus on flavor-changing currents that mediate transitions from one heavy
flavor to another. We stress differences in the formalism for heavy-light
currents, which are discussed in a companion paper, showing how HQET provides a
systematic matching procedure. We obtain one-loop results for the matching
factors of lattice currents, needed for heavy-quark phenomenology, such as the
calculation of zero-recoil form factors for the semileptonic decays . Results for the Brodsky-Lepage-Mackenzie scale are also
given.Comment: 35 pages, 17 figures. Program LatHQ2QCD to compute matching one-loop
coefficients available at http://theory.fnal.gov/people/kronfeld/LatHQ2QCD
Accumulating evidence for nonstandard leptonic decays of D_s mesons
The measured rate for D_s -> l nu decays, where l is a muon or tau, is larger
than the standard model prediction, which relies on lattice QCD, at the 3.8
sigma level. We discuss how robust the theoretical prediction is, and we show
that the discrepancy with experiment may be explained by a charged Higgs boson
or a leptoquark.Comment: 4 pages; v2 conforms with PRL versio
Monopole Spectra in non-Abelian Gauge Theories
We study the continuum limit of the length spectrum of magnetic monopole
structures found after various Abelian projections of pure gauge SU(2),
including the maximally Abelian gauge. We comment on Gribov copies, and
measurements of the string tension.Comment: Talk presented at LATTICE96(topology) LaTeX, with 4 LaTeX figure
Center Vortices, Instantons, and Confinement
We study the relation between center vortices and instantons in lattice QCD.Comment: 3 pages, 1 color figure, LaTeX209 using BoxedEPS and esprc2.sty
(provided); talk presented by J.W. Negele to be published in Lattice99
(Topology); email to [email protected]
Magnetic monopole clusters, and monopole dominance after smoothing in the maximally Abelian gauge of SU(2)
In the maximally Abelian gauge of SU(2), the clusters of monopole current are
found to divide into two distinct classes. The largest cluster permeates the
lattice, has a density that scales and produces the string tension. The
remaining clusters possess an approximate 1/l^3 number density distribution (l
is the cluster length), their radii vary as \sqrt l and their total current
density does not scale. Their contribution to the string tension is compatible
with being exactly zero. Their number density can be thought of as arising from
an underlying scale invariant distribution. This suggests that they are not
related to instantons. We also observe that when we locally smoothen the SU(2)
fields by cooling, the string tension due to monopoles becomes much smaller
than the SU(2) string tension. This dramatic loss of Abelian/monopole dominance
occurs even after just one cooling step.Comment: Talk presented at LATTICE97(topology). LaTeX, with 4 PS figure
DEPENDENCE OF THE CURRENT RENORMALISATION CONSTANTS ON THE QUARK MASS
We study the behaviour of the vector and axial current renormalisation
constants and as a function of the quark mass, . We show that
sizeable and systematic effects are present in the
Wilson and Clover cases respectively. We find that the prescription of
Kronfeld, Lepage and Mackenzie for correcting these artefacts is not always
successful.Comment: Contribution to Lattice'94, 3 pages PostScript, uuencoded compressed
Dual Superconductor Mechanism of Confinement on the Lattice
We investigate the dual superconductor mechanism of confinement for pure
SU(2) lattice gauge theory in the maximally abelian gauge. We focus on the the
dual Meissner effect. We find that the transverse distribution of the
longitudinal chromoelectric field due to a static quark-antiquark pair
satisfies the dual London equation. Moreover we show that the size of the flux
tube scales according to asymptotic freedom.Comment: LaTeX, 9 pages, 6 figures available as a PostScript file from L.
Cosmai, BARI - TH 110/9
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