Observation of an enhancement in e+e-→Υ(1S) πn+n-→Υ(2S)n+n- and (3S)n+n- production near s = 10.89 GeV

We measure the production cross sections for e + e - → Υ(1S)π + π - , Υ(2S)π + π - , and Υ(3S)π + π - as a function of √s between 10.83 GeV and 11.02 GeV. The data consist of 8.1 fb -1 collected with the Belle detector at the KEKB e + e - collider. We observe enhanced production in all three final states that does not agree well with the conventional Y(10860) line shape. A fit using a Breit-Wigner resonance shape yields a peak mass of [10888.4 +2.7 -2.6 (stat) ± 1.2(syst)] MeV/c 2 and a width of [30.7 +8.3 -7.0 (stat) ± 3.1 (syst)] MeV/c 2 .