Heavy Exotic Molecules with Charm and Bottom

TL;DR

This paper investigates heavy-light exotic molecules with charm and bottom, revealing their binding properties, chiral partner effects, and identifying known and potential new exotic states through theoretical modeling.

Contribution

It provides a detailed theoretical analysis of heavy-light exotic molecules, highlighting the effects of chiral partners and predicting specific bound states like the X(3872) and Z_b exotics.

Findings

Only charm isosinglet with J^{PC}=1^{++} binds, identified as X(3872)

Bottom isotriplet with J^{PC}=1^{+-} binds, related to Z_b states

Predicted a potential new neutral bottom exotic X_b(10532)

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 $J\leq 1$. 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.