Energy scan of the $e^+e^- \to h_b(nP)\pi^+\pi^-$ $(n=1,2)$ cross sections and evidence for $\Upsilon(11020)$ decays into charged bottomonium-like states

摘要: Using data collected with the Belle detector at the KEKB asymmetric-energy e+e− collider, we measure the energy dependence of the e+e−→hb(nP)π+π− (n=1,2) cross sections from thresholds up to 11.02GeV. We find clear Υ(10860) and Υ(11020) peaks with little or no continuum contribution. We study the resonant substructure of the Υ(11020)→hb(nP)π+π− transitions and find evidence that they proceed entirely via the intermediate isovector states Zb(10610) and Zb(10650). The relative fraction of these states is loosely constrained by the current data: the hypothesis that only Zb(10610) is produced is excluded at the level of 3.3 standard deviations, while the hypothesis that only Zb(10650) is produced is not excluded at a significant level.