Tata Institute of Fundamental Research, Mumbai 400005.
Phys Rev Lett. 2013 Sep 13;111(11):112001. doi: 10.1103/PhysRevLett.111.112001. Epub 2013 Sep 9.
We search for bottomonium states in Υ(2S) → (bb)γ decays with an integrated luminosity of 24.7 fb(-1) recorded at the Υ(2S) resonance with the Belle detector at KEK, containing (157.8±3.6)×10(6) Υ(2S) events. The (bb) system is reconstructed in 26 exclusive hadronic final states composed of charged pions, kaons, protons, and K(S)(0) mesons. We find no evidence for the state recently observed around 9975 MeV (X(bb)) in an analysis based on a data sample of 9.3×10(6) Υ(2S) events collected with the CLEO III detector. We set a 90% confidence level upper limit on the branching fraction B[Υ(2S) → X(bb)γ] × ∑(i)B[X(bb) → h(i)] < 4.9×10(-6), summed over the exclusive hadronic final states employed in our analysis. This result is an order of magnitude smaller than the measurement reported with CLEO data. We also set an upper limit for the ηb(1S) state of B[Υ(2S) → ηb(1S)γ] × ∑(i)B[ηb(1S) → h(i)] < 3.7×10(-6).
我们使用 Belle 探测器在 KEK 上对 Υ(2S)共振进行了实验，记录了 Υ(2S)→(bb)γ 衰变的总积分亮度为 24.7 fb(-1)，包含了(157.8±3.6)×10(6)个 Υ(2S)事件。在由带电π介子、K 介子、质子和 K(S)(0)介子组成的 26 个唯一的强子末态中，我们重建了(bb)系统。我们没有在基于 CLEO III 探测器收集的 9.3×10(6)个 Υ(2S)事件数据样本的分析中发现最近在 9975 MeV 左右观测到的状态(X(bb))的证据。我们对分支比 B[Υ(2S)→X(bb)γ]×∑(i)B[X(bb)→h(i)]<4.9×10(-6)设置了 90%置信水平的上限，其中∑(i)B[X(bb)→h(i)]是对我们分析中采用的唯一强子末态的求和。这个结果比 CLEO 数据报告的测量值小一个数量级。我们还对 ηb(1S)状态设置了上限，B[Υ(2S)→ηb(1S)γ]×∑(i)B[ηb(1S)→h(i)]<3.7×10(-6)。
