Flux-tube Structure, Sum Rules and Beta-functions in SU(2)

Action and energy flux-tube profiles are computed, in SU(2) with beta=2.4,2.5, for two quarks up to 1 fm apart and for which the colour fields are in their ground state (A_1g) and the first (E_u) and higher (A'_1g) excited gluonic states. When these profiles are integrated over all space, a scaling comparison is made between the beta=2.4 and 2.5 data. Using sum rules, these integrated forms also permit an estimate to be made of generalised beta-functions giving b(2.4)=-0.312(15), b(2.5)=-0.323(9), f(2.4)=0.65(1) and f(2.5)=0.68(1). When the profiles are integrated only over planes transverse to the interquark line and assuming underlying string features, scaling comparisons are again made near the centres of the interquark line for the largest interquark distances. For the A'_{1g} case, some of the profiles exhibit a 'dip-like' structure characteristic of the Isgur-Paton model.Comment: 3 pages, 6 eps figures. Presented at LATTICE9

Interactions of heavy-light mesons

The potential between static-light mesons forming a meson-meson or a meson-antimeson system is calculated in quenched and unquenched SU(3) gauge theory. We use the Sheikholeslami-Wohlert action and statistical estimators of light quark propagators with maximal variance reduction. The dependence of the potentials on the light quark spin and isospin and the effect of meson exchange is investigated. Our main motivation is exploration of bound states of two mesons and string breaking. The latter also involves the two-quark potential and the correlation between two-quark and two-meson states.Comment: Contribution to LATTICE99 (QCD spectrum). 3 pages, 4 eps figure

The radial distributions of a heavy-light meson on a lattice

In an earlier work, the charge (vector) and matter (scalar) radial distributions of heavy-light mesons were measured in the quenched approximation on a 16^3 times 24 lattice with a quark-gluon coupling of 5.7, a lattice spacing of 0.17 fm, and a hopping parameter corresponding to a light quark mass about that of the strange quark. Several improvements are now made: 1) The configurations are generated using dynamical fermions with a quark-gluon coupling of 5.2 (a lattice spacing of 0.14 fm); 2) Many more gauge configurations are included (78 compared with the earlier 20); 3) The distributions at many off-axis, in addition to on-axis, points are measured; 4) The data-analysis is much more complete. In particular, distributions involving excited states are extracted. The exponential decay of the charge and matter distributions can be described by mesons of mass 0.9+-0.1 and 1.5+-0.1 GeV respectively - values that are consistent with those of vector and scalar qqbar-states calculated directly with the same lattice parameters.Comment: 3 pages, 4 figures, Lattice2002(heavyquark

Four-quark energies in SU(2) lattice Monte Carlo using a tetrahedral geometry

This contribution -- a continuation of earlier work -- reports on recent developments in the calculation and understanding of 4-quark energies generated using lattice Monte Carlo techniques.Comment: 3 pages, latex, no figures, contribution to Lattice 9

The Charge and Matter radial distributions of Heavy-Light mesons calculated on a lattice

For a heavy-light meson with a static heavy quark, we can explore the light quark distribution. The charge and matter radial distributions of these heavy-light mesons are measured on a 16^3 * 24 lattice at beta=5.7 and a hopping parameter corresponding to a light quark mass about that of the strange quark. Both distributions can be well fitted up to 4 lattice spacings (r approx 0.7 fm) with the exponential form w_i^2(r), where w_i(r)=A exp(-r/r_i). For the charge(c) and matter(m) distributions r_c approx 0.32(2) fm and r_m approx 0.24(2) fm. We also discuss the normalisation of the total charge and matter integrated over all space, finding 1.30(5) and 0.4(1) respectively.Comment: 31 pages including 7 ps figure