Heavy Exotic Molecules with Charm and Bottom

Abstract

We revisit the formation of pion-mediated heavy-light exotic molecules with both charm and bottom and their chiral partners under the general strictures of both heavy-quark and chiral symmetry. The chiral exotic partners with good parity formed using the $(0^{+},1^{+})$ multiplet are about twice more bound than their primary exotic partners formed using the $(0^{-},1^{-})$ multiplet. The chiral couplings across the multiplets $(0^{\pm },1^{\pm })$ cause the chiral exotic partners to unbind, and the primary exotic molecules to be about twice more bound, for $J\le 1$. Our multi-channel coupling results show that only the charm isosinglet exotic molecules with $J^{PC}=1^{++}$ binds, which we identify as the reported neutral $X(3872)$. Also, the bottom isotriplet exotic with $J^{PC}=1^{+-}$ binds, which we identify as a mixture of the reported charged exotics $Z_b^{+}(10610)$ and $Z_b^{+}(10650)$. The bound isosinglet with $J^{PC}=1^{++}$ is suggested as a possible neutral $X_b(10532)$ not yet reported.

Comments: 10 pages, 9 figures