Imprint of the adjoint meson spectrum in the decay patterns of hidden-bottom tetraquarks

Abstract

We aim to clarify the experimentally observed near-degeneracy and decay patterns of the isospin, $I=1$, hidden-bottom tetraquarks $Z_b(10610)$ and $Z_b(10650)$ with quantum numbers $J^{P}=1^{+}$.We refer to them as $Z_b$ and $Z_b^{'}$, respectively. In particular, we find first evidence that the suppression of the decay of $Z_b^{'}$ to $B\bar{B^*}$ can be understood in the context of the Born-Oppenheimer Effective Field Theory (BOEFT). BOEFT enables writing both $Z_b$ and $Z_b^{'}$ as superpositions of $Z_1$ and $Z_2$ tetraquark configurations. This decomposition naturally relates the decay patterns of $Z_b$ and $Z_b^{'}$ to the degeneracy of the light degrees of freedom associated with $Z_1$ and $Z_2$ tetraquarks, {\it i.e.,} $1^{--}$and $0^{-+}$ adjoint mesons, respectively. By calculating the adjoint meson correlators within the framework of lattice QCD, we get good indications that these adjoint mesons are degenerate.

Figures (1)

• Figure 1: This figure shows preliminary effective masses of six $I=1$ adjoint mesons (see text for details). Adjoint mesons with continuum quantum numbers $0^{-+}$ and $1^{--}$ are associated with $S\text{-wave}+S\text{-wave}$ heavy-light thresholds, whereas the adjoint mesons carrying continuum quantum numbers $1^{++}$, $0^{+-}$, $0^{++}$ and $1^{+-}$ are associated with $S\text{-wave}+P\text{-wave}$ heavy-light thresholds. The mapping of continuum quantum numbers to their lattice counterparts is given in Tab. \ref{['tab:map']}.