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±,1±) cause the chiral exotic partners to unbind, and the primary exotic molecules to be about twice more bound, for J≤1. Our multi-channel coupling results show that only the charm isosinglet exotic molecules with JPC=1++ bind, which we identify as the reported neutral X(3872). Also, the bottom isotriplet exotic with JPC=1+− binds, which we identify as a mixture of the reported charged exotics Zb+(10610) and Zb+(10650). The bound isosinglet with JPC=1++ is suggested as a possible neutral Xb(10532) not yet reported.