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arXiv · 0710.2577

Observation of anomalous Upsilon(1S)pi+pi- and Upsilon(2S)pi+pi- production near the Upsilon(5S) resonance

The Belle Collaboration·K. -F. Chen·W. -S. Hou·M. Shapkin·A. Sokolov et al
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Abstract

We report the first observation of e+e- -> Upsilon(1S)pi+pi-, Upsilon(2S)pi+pi-, and first evidence for e+e- -> Upsilon(3S)pi+pi-, Upsilon(1S)K+K-, near the peak of the Upsilon(5S) resonance at sqrt{s}~10.87 GeV. The results are based on a data sample of 21.7 fb^-1 collected with the Belle detector at the KEKB e+e- collider. Attributing the signals to the Upsilon(5S) resonance, the partial widths Gamma(Upsilon(5S) -> Upsilon(1S) pi+pi-) = 0.59 +- 0.04 (stat) +- 0.09 (syst) MeV and Gamma(Upsilon(5S) -> Upsilon(2S) pi+pi-) = 0.85 +- 0.07 (stat) +- 0.16 (syst) MeV are obtained from the observed cross sections. These values exceed by more than two orders of magnitude the previously measured partial widths for dipion transitions between lower Upsilon resonances.

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The Belle Collaboration, K. -F. Chen, W. -S. Hou, M. Shapkin, A. Sokolov et al. 2009-10-26. Observation of anomalous Upsilon(1S)pi+pi- and Upsilon(2S)pi+pi- production near the Upsilon(5S) resonance. https://doi.org/10.1103/physrevlett.100.112001

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