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

Abstract

We report the first observation of e(+)e(-) -> Y(1S)pi(+)pi(-), Upsilon(2S)pi(+)pi(-), and first evidence for e(+)e(-) -> Y(3S)pi(+)pi(-), Y(1S)K+K-, near the peak of the Y(5S) resonance at root s similar to 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(Y(5S) -> Y(1S)pi(+)pi(-)) = 0.59 +/- 0.04(stat)+/- 0.09(syst) MeV and Gamma(Y(5S) -> Y(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 2 orders of magnitude the previously measured partial widths for dipion transitions between lower Y resonances.