13 research outputs found
Structure functions near the chiral limit
We compute hadron masses and the lowest moments of unpolarized and polarized
nucleon structure functions down to pion masses of 300 MeV, in an effort to
make unambiguous predictions at the physical light quark mass.Comment: 3 pages, 3 figures, Lattice2002(matrixel
Study of unstable particle through the spectral function in O(4) theory
We test application of the maximum entropy method to decompose the states
contributing to the unstable correlation function through the spectral
function in the four dimensional O(4) theory. Reliable results are
obtained for the mass and two-particle state energy using
only the correlation function. We also find that the property of the
particle is different between the unstable ()
and stable () cases.Comment: Lattice2002(spectrum), 3 page
A non-perturbative determination of Z_V and b_V for O(a) improved quenched and unquenched Wilson fermions
By considering the local vector current between nucleon states and imposing
charge conservation we determine, for improved Wilson fermions, its
renormalisation constant and quark mass improvement coefficient. The
computation is performed for both quenched and two flavour unquenched fermions.Comment: 3 pages, 4 figures, Lattice(2002)(improve
A Study of Charmonium Systems across the Deconfinement Transition
We present results from lattice studies of charmonium systems near the
deconfinement transition temperature. On quenched isotropic lattices with
lattice spacings between 0.02 and 0.05 fm, bar{q} q systems with quark masses
close to the charm mass and with different spin-parity quantum numbers are
studied in the temperature range 0.9 Tc - 3 Tc. Results for temporal
correlators of local operators, and the spectral functions constructed from
them, are discussed. For the pseudoscalar and vector channels, the correlators
are observed to change very little across the deconfinement transition, unlike
in the case of the light quarks.Comment: 3 pages, 4 figures, Lattice2002(nonzerot
International Lattice Data Grid
We propose the co-ordination of lattice QCD grid developments in different
countries to allow transparent exchange of gauge configurations in future,
should participants wish to do so. We describe briefly UKQCD's XML schema for
labelling and cataloguing the data. A meeting to further develop these ideas
will be held in Edinburgh on 19/20 December 2002, and will be available over
AccessGrid.Comment: Lattice2002(plenary
Excited Baryons from the FLIC Fermion Action
Masses of positive and negative parity excited nucleons and hyperons are
calculated in quenched lattice QCD using an O(a^2) improved gluon action and a
fat-link clover fermion action in which only the irrelevant operators are
constructed with fat links. The results are in agreement with earlier N*
simulations with improved actions, and exhibit a clear mass splitting between
the nucleon and its parity partner, as well as a small mass splitting between
the two low-lying J^P={1/2}^- N* states. Study of different Lambda
interpolating fields suggests a similar splitting between the lowest two
{1/2}^- Lambda* states, although the empirical mass suppression of the
Lambda*(1405) is not seen.Comment: 3 pages, 3 figures, Lattice2002(QCD Spectrum and Quark Masses
Chiral Effective Lagrangian and Quark Masses
The status of lattice determinations of quark masses is reviewed (with the
exception of m_b). Attempts to extract the low-energy constants in the
effective chiral Lagrangian are discussed, with special emphasis on those
couplings which are required to test the hypothesis of a massless up-quark.
Furthermore, the issue of quenched chiral logarithms is addressed.Comment: Invited talk presented at Lattice2002(plenary), 12 pages, 3 figure
Spin-3/2 baryons in lattice QCD
Copyright © 2003. Elsevier. Printed in U.S.A. Submitted to Cornell University’s online archive www.arXiv.org in 2003 by James Zanotti. Post-print sourced from www.arxiv.org.We present first results for masses of spin-3/2 baryons in lattice QCD, using a novel fat-link clover fermion action in which only the irrelevant operators are constructed using fat links. In the isospin-1/2 sector, we observe, after appropriate spin and parity projection, a strong signal for the J^P=3/2^- state, and find good agreement between the 1/2^+ mass and earlier nucleon mass simulations with a spin-1/2 interpolating field. For the isospin-3/2 Delta states, clear mass splittings are observed between the various 1/2^+/- and 3/2^+/- channels, with the calculated level orderings in good agreement with those observed empirically.J.M. Zanotti, S. Choe, D.B. Leinweber, W. Melnitchouk, A.G. Williams, and J.B. Zhanghttp://www.elsevier.com/wps/find/journaldescription.cws_home/505717/description#descriptio
Quenched QCD with fixed-point and chirally improved fermion
In this contribution we present results from quenched QCD simulations with
the parameterized fixed-point (FP) and the chirally improved (CI) Dirac
operator. Both these operators are approximate solutions of the Ginsparg-Wilson
equation and have good chiral properties. We focus our discussion on
observables sensitive to chirality. In particular we explore pion masses down
to 210 MeV in light hadron spectroscopy, quenched chiral logs, the pion decay
constant and the pion scattering length. We discuss finite volume effects,
scaling properties of the FP and CI operators and performance issues in their
numerical implementation.Comment: Lattice2002(chiral), 17 pages, 21 figures, (LaTeX style file
espcrc2.sty and AMS style files