American Physical Society, Physical Review Letters, 14(117), 2016
DOI: 10.1103/physrevlett.117.142001
Full text: Download
Using data collected with the Belle detector at the KEKB asymmetric-energy$e^{+}e^{-}$ collider, we measure the energy dependence of the $e^{+}e^{-}\to h_{b}(nP)π^{+}π^{-}$ (n=1, 2) cross sections from thresholds up to 11.02 GeV. We find clear ϒ(10860) and ϒ(11020) peaks with little or no continuum contribution. We study the resonant substructure of the ϒ(11020)$\to h_{b}(nP)π^{+}π^{-}$ transitions and find evidence that they proceed entirely via the intermediate isovector states Z$_b$(10610) and Z$_b$(10650). The relative fraction of these states is loosely constrained by the current data: The hypothesis that only Z$_b$(10610) is produced is excluded at the level of 3.3 standard deviations, while the hypothesis that only Z$_b$(10650) is produced is not excluded at a significant level.