Searching for dynamical fermion effects in UKQCD simulations

We present recent results from the UKQCD collaboration's dynamical QCD simulations. This data has fixed lattice spacing but varying dynamical quark mass. We concentrate on searching for an unquenching signal in the mesonic mass spectrum where we do not find a significant effect at the quark masses considered.Comment: 3 pages, 3 figures, Lattice2001(spectrum

Light Quenched Hadron Spectrum and Decay Constants on different Lattices

We present a study of ${\cal O}(2000)$ (quenched) lattice configurations from the APE collaboration, for $6.0\le\beta\le 6.4$ using both the Wilson and the SW-Clover fermion action. We determine the light hadronic spectrum and meson decay constants. We extract the inverse lattice spacing using data at the simulated values of the quark mass. We find an agreement with the experimental data of $\sim 5$ for mesonic masses and $\sim 10$ for baryonic masses and pseudoscalar decay constants. A larger deviation is present for the vector decay constants.Comment: 3 pages, Talk presented at LATTICE96(spectrum

An analysis of the vector meson spectrum from lattice QCD

We re-analyse meson sector data from the CP-PACS collaboration's dynamical simulations. Our analysis uses several different approaches, and compares the standard naive linear fit with the Adelaide Anzatz. We find that setting the scale using the J parameter gives remarkable agreement among data sets. Our predictions for the rho and phi masses have very small statistical errors, ~ 3 MeV, but the discrepancy between the different fitting approaches is ~ 40 MeV.Comment: 3 pages, 4 figures, 3 tables, proceedings for Lattice2003(Spectrum

Effects of Dynamical Quarks in UKQCD Simulations

Recent results from the UKQCD Collaboration's dynamical simulations are presented. The main feature of these ensembles is that they have a fixed lattice spacing and volume, but varying sea quark mass from infinite (corresponding to the quenched simulation) down to roughly that of the strange quark mass. The main aim of this work is to uncover dynamical quark effects from these ``matched'' ensembles. We obtain some evidence of dynamical quark effects in the static quark potential with less effects in the hadronic spectrum.Comment: Invited paper presented at the Workshop on Lattice Hadron Physics, July 2001, Cairns, Australia. 7 pages. Uses espcrc2.sty (included

RESULTS FOR THE B-MESON DECAY CONSTANT FROM THE APE COLLABORATION

The decay constant for the B-meson in the static limit is calculated using the Wilson and clover actions at various lattice spacings. We show that both the contamination of our results by excited states and the effects finite lattice spacing are at most the order of the statistical uncertainties. A comparison is made of our results and those obtained in other studies. Values for $f^{stat}_{B_S}/f^{stat}_B$ and $M_{B_S} - M_B$ are also given.Comment: Contribution to Lattice'94, 3 pages PostScript, uuencoded compresse

Light Quark Mass Determinations from the Lattice

This paper is a review of recent lattice determinations of the light quark masses. It describes the method employed to calculate quark masses in the lattice formulation, and the extrapolations required to reach the physical regime. This review is designed to be accessible to a general audience, not specifically lattice theorists.Comment: Invited review talk at QCD97, Montpellier (July '97). 8 pages, 2 figures. Requires espcrc2.sty Minor changes: a reference added and a table updated accordingl

Recent Lattice QCD Results from the UKQCD Collaboration

The lattice technique of studying the strong interaction of matter is used to obtain predictions of the hadronic spectrum. These simulations were performed by the UKQCD collaboration using full (unquenched) QCD. Details of the results, a comparison with quenched data, and novel methods of extracting spectral properties are described.Comment: Paper presented at the Computational Physics Conference CCP2000, 3-8 Decmeber 2000, Gold Coast, Australia, 5 pages, 3 figure

A High Statistics Lattice Calculation of Quark Masses with a Non-Perturbative Renormalization Procedure

We present results of a high statistics study (O(2000) configurations) of the quark masses in the MS-bar scheme from Lattice QCD in the quenched approximation at beta=6.0, beta=6.2 and beta=6.4 using both the Wilson and the tree-level improved SW-Clover fermion action. We extract quark masses from the meson spectroscopy and from the axial Ward Identity using non-perturbative values of the renormalization constants. We compare the results obtained with the two methods and we study the O(a) dependence of the quark masses for both actions. Our best results are m_s^(MS-bar)(2 GeV)=(123 +- 4 +- 15) MeV and m_c^(MS-bar)(2 GeV)=(1525 +- 40 +- 100) MeV.Comment: 3 pages, Talk presented at LATTICE97(QCD Spectrum and Quark Masses). Small misprints corrected, no conclusions change

Lattice QCD with Dynamical Quarks from the UKQCD Collaboration

A brief overview of the lattice technique of studying QCD is presented. Recent results from the UKQCD Collaboration's simulations with dynamical quarks are then presented. In this work, the calculations are all at a fixed lattice spacing and volume, but varying sea quark mass from infinite (corresponding to the quenched simulation) down to roughly that of the strange quark mass. The main aim of this work is to uncover dynamical quark effects from these ``matched'' ensembles.Comment: Invited paper presented at the International Light-Cone Workshop "Light-cone Physics: Particles and Strings", September 2001, Trento, Italy. 7 page

Spectral Functions, Maximum Entropy Method and Unconventional Methods in Lattice Field Theory

We present two unconventional methods of extracting information from hadronic 2-point functions produced by Monte Carlo simulations. The first is an extension of earlier work by Leinweber which combines a QCD Sum Rule approach with lattice data. The second uses the Maximum Entropy Method to invert the 2-point data to obtain estimates of the spectral function. The first approach is applied to QCD data, and the second method is applied to the Nambu--Jona-Lasinio model in (2+1)D. Both methods promise to augment the current approach where physical quantities are extracted by fitting to pure exponentials.Comment: Paper presented at the Workshop on Lattice Hadron Physics, July 2001, Cairns, Australia. 5 pages. Minor spelling error correcte