A model for multi-quark systems

As a step towards understanding multi-quark systems abundant in nature we construct a model that reproduces the binding energies of static four-quark systems. These energies have been calculated using SU(2) lattice gauge theory for a set of six different geometries representative of the general case. The model is based on ground and excited state two-body potentials and multi-quark interaction terms.Comment: 10 pages, one LaTeX figur

An interquark potential model for multi-quark systems

A potential model for four interacting quarks is constructed in SU(2) from six basis states -- the three partitions into quark pairs, where the gluon field is either in its ground state or first excited state. With four independent parameters to describe the interactions connecting these basis states, it is possible to fit 100 pieces of data -- the ground and first excited states of configurations from six different four-quark geometries calculated on a 16^3*32 lattice.Comment: 14 page

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

Can lattice data for two heavy-light mesons be understood in terms of simply two-quark potentials?

By comparing lattice data for the two heavy-light meson system (Q^2 qbar^2) with a standard many-body approach employing only interquark potentials, it is shown that the use of unmodified two-quark potentials leads to a gross overestimate of the binding energy.Comment: Contribution to LATTICE99 (Heavy Quarks). 3 pages, 2 ps 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