A variational fit to the lattice energy of two heavy-light mesons

Recent lattice calculations on the interaction energy of two heavy-light mesons (Q^2\bar{q}^2) are interpreted in terms of the potential of the corresponding single heavy-light meson (Q\bar{q}). This model leads to a large overestimate of the binding compared with the lattice data -- unless the basic Q\bar{q} potential is modified to become a four-quark potential.