The isovector bottomoniumlike exotic resonances $Z_b(10610)$ and $Z_b(10650)$ are very close to the thresholds of heavy meson pairs $B{\overline{B}}^{*}(\overline{B}{B}^{*})$ and $B^{*}{\overline{B}}^{*}$, and are naturally understood as “molecular” states made of the corresponding meson-antimeson pairs. The picture with a full separation of the two channels cannot be exact and a cross-feed between the states necessarily takes place. A simple model is considered here describing the mixing between the channels in terms of one parameter. The model reasonably describes the current data on the decays of the $Z_b$ resonances to bottomonium plus a pion and predicts the rate and a distinctive interference pattern for the decay $Z_b(10650)\to B{\overline{B}}^{*}(\overline{B}{B}^{*})$ as well as excess of the mass splitting between the resonances over the mass difference between $B^{*}$ and $B$ mesons.

• Received 19 July 2017

DOI:https://doi.org/10.1103/PhysRevD.96.094024