Energy Scan of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{h}_{b}(nP){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ ($n=1$, 2) Cross Sections and Evidence for $\mathrm{\ensuremath{\Upsilon}}(11020)$ Decays into Charged Bottomoniumlike States

Energy Scan of the $e^{+} e^{-} \to h_{b} (n P) π^{+} π^{-}$ ( $n = 1$ , 2) Cross Sections and Evidence for $ϒ (11020)$ Decays into Charged Bottomoniumlike States

R. Mizuk et al. (Belle Collaboration)

Phys. Rev. Lett. 117, 142001 – Published 28 September 2016

Abstract

Using data collected with the Belle detector at the KEKB asymmetric-energy $e^{+} e^{-}$ collider, we measure the energy dependence of the $e^{+} e^{-} \to h_{b} (n P) π^{+} π^{-}$ ( $n = 1$ , 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 $ϒ (11020) \to h_{b} (n P) π^{+} π^{-}$ 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.