# Observation of $\Upsilon(4S)$ decays to $\pi^+\pi^-\Upsilon(1S)$ and $\pi^+\pi^-\Upsilon(2S)$

Abstract : We present the first measurement of $\Upsilon(4S)$ decays to $\pi^+\pi^-\Upsilon(1S)$ and $\pi^+\pi^-\Upsilon(2S)$ based on a sample of 230$\times10^6$ $\Upsilon(4S)$ mesons collected with the BABAR detector. We measure the product branching fractions ${\cal B}(\Upsilon(4S)\to \pi^+\pi^-\Upsilon(1S))\times{\cal B}(\Upsilon(1S)\to\mu^+\mu^-)=(2.23\pm0.25_{stat} \pm0.27_{sys})\times 10^{-6}$ and ${\cal B}(\Upsilon(4S)\to \pi^+\pi^-\Upsilon(2S))\times{\cal B}(\Upsilon(2S)\to\mu^+\mu^-)=(1.69\pm0.26_{stat}\pm0.20_{sys})\times 10^{-6}$, from which we derive the partial widths $\Gamma(\Upsilon(4S)\to \pi^+\pi^-\Upsilon(1S))=(1.8\pm0.4)$~keV and $\Gamma(\Upsilon(4S)\to \pi^+\pi^-\Upsilon(2S))=(2.7\pm0.8)$~keV.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00084384
Contributor : Claudine Bombar <>
Submitted on : Wednesday, January 17, 2007 - 10:29:00 AM
Last modification on : Wednesday, September 16, 2020 - 4:25:14 PM

### Citation

B. Aubert, R. Barate, D. Boutigny, F. Couderc, Y. Karyotakis, et al.. Observation of $\Upsilon(4S)$ decays to $\pi^+\pi^-\Upsilon(1S)$ and $\pi^+\pi^-\Upsilon(2S)$. Physical Review Letters, American Physical Society, 2006, 96, pp.232001. ⟨10.1103/PhysRevLett.96.232001⟩. ⟨in2p3-00084384⟩

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