Exotic [formula omitted] states in QCD

Abstract

QCD contains stable four-quark QQ qq hadronic states in the limit where the heavy quark mass goes to infinity. (Here Q denotes a heavy quark, q a light antiquark and the stability refers only to the strong interactions.) The long-range binding potential is due to one-pion exchange between ground state Q q mesons, and is computed using chiral perturbation theory. For the Q = b, this long-range potential may be sufficiently attractive to produce a weakly bound two-meson state.