Phys. Rev. D 70, 032001 (2004) [7 pages]First observation of a Υ(1D) stateReceived 16 April 2004; published 16 August 2004 We present the first evidence for the production of Υ(1D) states in the four-photon cascade, Υ(3S)→γχb(2P), χb(2P)→γΥ(1D), Υ(1D)→γχb(1P), χb(1P)→γΥ(1S), followed by the Υ(1S) annihilation into e+e- or μ+μ-. The signal has a significance of 10.2 standard deviations. The measured product branching ratio for these five decays, (2.5±0.5±0.5)×10-5, is consistent with the theoretical estimates. The data are dominated by the production of one Υ(1D) state consistent with the J=2 assignment. Its mass is determined to be (10161.1±0.6±1.6) MeV, which is consistent with the predictions from potential models and lattice QCD calculations. We also searched for Υ(3S)→γχb(2P), χb(2P)→γΥ(1D), followed by either Υ(1D)→ηΥ(1S) or Υ(1D)→π+π-Υ(1S). We find no evidence for such decays and set upper limits on the product branching ratios. © 2004 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevD.70.032001
DOI:
10.1103/PhysRevD.70.032001
PACS:
14.40.Gx, 13.20.Gd
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