109 research outputs found

### A Study of Degenerate Four-quark states in SU(2) Lattice Monte Carlo

The energies of four-quark states are calculated for geometries in which the
quarks are situated on the corners of a series of tetrahedra and also for
geometries that correspond to gradually distorting these tetrahedra into a
plane. The interest in tetrahedra arises because they are composed of {\bf
three } degenerate partitions of the four quarks into two two-quark colour
singlets. This is an extension of earlier work showing that geometries with
{\bf two} degenerate partitions (e.g.\ squares) experience a large binding
energy. It is now found that even larger binding energies do not result, but
that for the tetrahedra the ground and first excited states become degenerate
in energy. The calculation is carried out using SU(2) for static quarks in the
quenched approximation with $\beta=2.4$ on a $16^3\times 32$ lattice. The
results are analysed using the correlation matrix between different euclidean
times and the implications of these results are discussed for a model based on
two-quark potentials.Comment: Original Raw PS file replace by a tarred, compressed and uuencoded PS
fil

### Hybrid Meson Potentials and the Gluonic van der Waals Force

The chromoelectric polarizability of mesons governs the strength of the
gluonic van der Waals force and therefore of non-quark-exchange processes in
hadronic physics. We compute the polarizability of heavy mesons with the aid of
lattice gauge theory and the Born--Oppenheimer adiabatic expansion. We find
that the operator product expansion breaks down at surprisingly large quarks
masses due to nonperturbative gluodynamics and that previous conclusions
concerning $J/\psi$--nuclear matter interactions and $J/\psi$ dissociation in
the quark-gluon plasma must be substantially modified.Comment: 5 pages, RevTex, 2 ps figures. Version to appear in Phys. Lett.

### Confinement, Crossing Symmetry, and Glueballs

We suggest that the quark-confining force is related by crossing symmetry to
a color-singlet glueball ${\cal G}$ which is well described as a loop of one
quantum of color magnetic flux. Electron pair annihilation as high as $\approx
2 GeV$ above the $\Upsilon$ mass could produce $\Upsilon \rightarrow
\ell^+\ell^-$ accompanied by ${\cal G}$ or one of its excited states.Comment: LaTeX, 12 pages, no figures, Los Alamos preprint LA-UR-94-263

### An Analysis of Four-quark Energies in SU(2) Lattice Monte Carlo using the Flux-tube Symmetry:

Energies of four-quark systems calculated by the static quenched SU(2)
lattice Monte Carlo method are analyzed in $2\times 2$ bases for square,
rectangle, tilted rectangle, linear and quadrilateral geometry configurations
and in $3\times 3$ bases for a non-planar geometry configuration. For small
interquark distances, a lattice effect is taken into account by considering
perimeter dependent terms which are characterized by the cubic symmetry. It is
then found that a parameter $f$ - that can be identified as a gluon field
overlap factor - is rather well described by the form $exp(-[b_sE{\cal
A}+\sqrt{b_s}F{\cal P}])$, where ${\cal A}$ and ${\cal P}$ are the area and
perimeter mainly defined by the positions of the four quarks, $b_s$ is the
string constant in the 2-quark potentials and $E,F$ are constants.Comment: (19 pages of Latex - 1 page of figures not included - sent on
request). Preprint HU-TFT-94-2

### Orbitally excited and hybrid mesons from the lattice

We discuss in general the construction of gauge-invariant non-local meson
operators on the lattice. We use such operators to study the $P$- and $D$-wave
mesons as well as hybrid mesons in quenched QCD, with quark masses near the
strange quark mass. The resulting spectra are compared with experiment for the
orbital excitations. For the states produced by gluonic excitations (hybrid
mesons) we find evidence of mixing for non-exotic quantum numbers. We give
predictions for masses of the spin-exotic hybrid mesons with $J^{PC}=1^{-+},\
0^{+-}$, and$2^{+-}$.Comment: 31 pages, LATEX, 8 postscript figures. Reference adde

### Efficient Hadronic Operators in Lattice Gauge Theory

We study operators to create hadronic states made of light quarks in quenched
lattice gauge theory. We construct non-local gauge-invariant operators which
provide information about the spatial extent of the ground state and excited
states. The efficiency of the operators is shown by looking at the wave
function of the first excited state, which has a node as a function of the
spatial extent of the operator. This allows one to obtain an uncontaminated
ground state for hadrons.Comment: 18 pages, Latex text, followed by 11 postscript figures in
self-unpacking file. Also available at
ftp://suna.amtp.liv.ac.uk/pub/cmi/wavefn

### Heavy Quarkonia from Anisotropic and Isotropic Lattices

We report on recent results for the spectrum of heavy quarkonia. Using coarse
and anisotropic lattices we achieved an unprecedented control over statistical
and systematic errors for higher excited states such as exotic hybrid states.
In a parallel study on isotropic lattices we also investigate the effect of two
dynamical flavours on the spin structure of charmonium and bottomonium for
several symmetric lattices.Comment: LATTICE'99 (heavy quarks), 3 pages, 3 figure

### Exotic Quarkonia from Anisotropic Lattices

We study in detail the spectrum of heavy quarkonia with different orbital
angular momentum along with their radial and gluonic excitations. Using an
anisotropic formulation of Lattice QCD we achieved an unprecedented control
over statistical errors and were able to study systematic errors such as
lattice spacing artefacts, finite volume effects and relativistic corrections.
First results on the spin structure in heavy hybrids are also presented.Comment: 4 pages, 4 figure

### Observing Long Colour Flux Tubes in SU(2) Lattice Gauge Theory

We present results of a high statistics study of the chromo field
distribution between static quarks in SU(2) gauge theory on lattices of volumes
16^4, 32^4, and 48^3*64, with physical extent ranging from 1.3 fm up to 2.7 fm
at beta=2.5, beta=2.635, and beta=2.74. We establish string formation over
physical distances as large as 2 fm. The results are tested against Michael's
sum rules. A detailed investigation of the transverse action and energy flux
tube profiles is provided. As a by-product, we obtain the static lattice
potential in unpreceded accuracy.Comment: 66 pages, 29 figures, uuencoded latex file with epsfigures (450 K),
supplementary full colour figures are available via ftp, CERN-TH.7413/94
(extended version

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