First observation of the hadronic transition ${\rm Y}(4S)\to \eta h_b(1P)$ and new measurement of the $h_b(1P)$ and ${\eta }_b(1S)$ parameters

Abstract

Using a sample of $771.6\times 10^6$ ${\rm Y}(4S)$ decays collected by the Belle experiment at the KEKB $e^{+}{e}^{-}$ collider, we observe for the first time the transition ${\rm Y}(4S)\to \eta h_b(1P)$ with the branching fraction $\mathcal{B}[{\rm Y}(4S)\to \eta h_b(1P)]=(2.18\pm 0.11\pm 0.18)\times 10^{-3}$ and we measure the $h_b(1P)$ mass $M_{h_b(1P)}=(9899.3\pm 0.4\pm 1.0)$ MeV/$c^2$, corresponding to the hyperfine splitting $\Delta M_{\mathrm{H}F}(1P)=(0.6\pm 0.4\pm 1.0)$ MeV/$c^2$. Using the transition $h_b(1P)\to \gamma {\eta }_b(1S)$, we measure the ${\eta }_b(1S)$ mass $M_{{\eta }_b(1S)}=(9400.7\pm 1.7\pm 1.6)$ MeV/$c^2$, corresponding to $\Delta M_{\mathrm{H}F}(1S)=(59.6\pm 1.7\pm 1.6)$ MeV/$c^2$, the ${\eta }_b(1S)$ width ${\Gamma }_{{\eta }_b(1S)}=(8_{-5}^{+6}\pm 5)$ MeV/$c^2$ and the branching fraction $\mathcal{B}[h_b(1P)\to \gamma {\eta }_b(1S)]=(56\pm 8\pm 4)\%$.

7 pages, 2 figures, submitted to Phys. Rev. Lett

References in corpus (5)

• Big-Bang Nucleosynthesis
• Heavy quarkonium: progress, puzzles, and opportunities
• Charmonium
• ${\rm Y}(4S,5S)\to {\rm Y}(1S)\eta$ transitions in the rescattering model and the new BaBar measurement
• Extracting the light quark mass ratio m_u/m_d from bottomonia transitions

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