We report the first observation of e+e-→Υ(1S)π+π-, Υ(2S)π+π-, and first evidence for e+e-→Υ(3S)π+π-, Υ(1S)K+K-, near the peak of the Υ(5S) resonance at s∼10.87GeV. The results are based on a data sample of 21.7fb-1 collected with the Belle detector at the KEKB e+e- collider. Attributing the signals to the Υ(5S) resonance, the partial widths Γ(Υ(5S)→Υ(1S)π+π-)=0. 59±0.04(stat)±0.09(syst)MeV and Γ(Υ(5S)→Υ(2S) π+π-)=0.85±0.07(stat)±0.16(syst)MeV are obtained from the observed cross sections. These values exceed by more than 2 orders of magnitude the previously measured partial widths for dipion transitions between lower Υ resonances.
ASJC Scopus subject areas
- Physics and Astronomy(all)