CLNS 98/1576 CLEO 98-12 Υ dipion transitions at energies near the Υ(4S).
نویسندگان
چکیده
Using a 4.19 fb−1 data sample collected with the CLEO II detector at the Cornell Electron Storage Ring, we have searched for dipion transitions between pairs of Υ resonances at center of mass energies Ecm = 10.58 GeV and Ecm = 10.52 GeV. We obtain the 90% confidence level upper limits B(Υ(4S) → Υ(2S)π+π−) < 3.9 × 10−4 and B(Υ(4S) → Υ(1S)π+π−) < 1.2 × 10−4. We also observe the transitions Υ(3S) → Υ(1S)π+π−, Υ(3S) → Υ(2S)π+π−, and Υ(2S) → Υ(1S)π+π−, from which we measure the cross-sections for the radiative processes e+e− → Υ(3S)γ and e+e− → Υ(2S)γ. We obtain σee→Υ(3S)γ = (17.5 ± 3.0 ± 1.6) pb and σee→Υ(2S)γ = (15.5 ± 1.3 ± 1.3) pb at Ecm = 10.58 GeV, and σee→Υ(3S)γ = (27.3 ± 5.0 ± 2.5) pb and σee→Υ(2S)γ = (16.3± 1.8± 1.3) pb at Ecm = 10.52 GeV, which we compare with theoretical predictions.
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