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

Understand

We report the study of e+e- -> Upsilon(1S)pi+pi-, Upsilon(2S)pi+pi-, Upsilon(3S)pi+pi-, and Upsilon(1S)K+K-, near the peak of the Upsilon(5S) resonance.

• 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.