Heavy Holographic Exotics: Tetraquarks as Efimov States

Abstract

We provide a holographic description of non-strange multiquark exotics as compact topological molecules by binding heavy-light mesons to a tunneling configuration in D8-D$\bar{8}$ that is homotopic to the vacuum state with fixed Chern-Simons number. In the tunneling process, the heavy-light mesons transmute to fermions. Their binding is generic and arises from a trade-off between the dipole attraction induced by the Chern-Simons term and the U(1) fermionic repulsion. In the heavy quark limit, the open-flavor tetraquark exotics $QQ\bar{q}\bar{q}$ and $\bar{Q}\bar{Q}qq$, emerge as bound Efimov states in a degenerate multiplet $I{J}^{\pi }=(00^{+},01^{+})$ with opposite intrinsic Chern-Simons numbers $\pm \frac{1}{2}$. The hidden-flavor tetraquark exotics such as $Q\bar{Q}q\bar{q}$, $QQ\bar{Q}\bar{q}$ and $QQ\bar{Q}\bar{Q}$ as compact topological molecules are unbound. Other exotics are also discussed.

Comments: 16 pages, 13 figures