The QCD String Spectrum and Conformal Field Theory

The low energy excitation spectrum of the critical Wilson surface is discussed between the roughening transition and the continuum limit of lattice QCD. The fine structure of the spectrum is interpreted within the framework of two-dimensional conformal field theory.Comment: Lattice2001 (confinement),3 pages,1 figure,uses espcrc2.st

Coulomb energy and gluon distribution in the presence of static sources

We compute the energy of the ground state and a low lying excitation of the gluonic field in the presence of static quark -anti-quark (\qq) sources. We show that for separation between the sources less then a few fm the gluonic ground state of the static \qq system can be well described in terms of a mean field wave functional with the excited states corresponding to a single quasi-particle excitation of the gluon field. We also discuss the role of many particle excitations relevant for large separation between sources.Comment: 14 pages, 11 figure

Multi-hadron states in Lattice QCD spectroscopy

The ability to reliably measure the energy of an excited hadron in Lattice QCD simulations hinges on the accurate determination of all lower-lying energies in the same symmetry channel. These include not only single-particle energies, but also the energies of multi-hadron states. This talk deals with the determination of multi-hadron energies in Lattice QCD. The group-theoretical derivation of lattice interpolating operators that couple optimally to multi-hadron states is described. We briefly discuss recent algorithmic developments which allow for the efficient implementation of these operators in software, and present numerical results from the Hadron Spectrum Collaboration.Comment: 5 pages, 3 figures, talk given at Hadron 2009, Tallahassee, Florida, December 1, 200

Charmonium excited state spectrum in lattice QCD

Working with a large basis of covariant derivative-based meson interpolating fields we demonstrate the feasibility of reliably extracting multiple excited states using a variational method. The study is performed on quenched anisotropic lattices with clover quarks at the charm mass. We demonstrate how a knowledge of the continuum limit of a lattice interpolating field can give additional spin-assignment information, even at a single lattice spacing, via the overlap factors of interpolating field and state. Excited state masses are systematically high with respect to quark potential model predictions and, where they exist, experimental states. We conclude that this is most likely a result of the quenched approximation.Comment: Fixed typos: normalisation of chi-squared, some operator projections in appendix, missing lattice irrep tabl

A study of hybrid quarkonium using lattice QCD

The hybrid quarkonium states are studied using the Born-Oppenheimer expansion. The first step in this expansion is the determination of the energy levels of the gluons in the presence of a static quark-antiquark pair as a function of the quark-antiquark separation. The spectrum of such gluonic excitations is determined from first principles using lattice QCD.Comment: to appear in Proceedings of HADRON97, BNL, August 1997, edited by S.U. Chung, AIP press; 4 pages, Latex, uses aipproc.sty, 2 postscript figure