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arXiv 1012.0481hep-ex
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辐射B^0 -> K^0 γ衰变的观测及其随时间的CP破坏测量

Observation of Radiative B^0 -> ϕK^0 γDecays and Measurements of Their Time-Dependent CP Violation

H. Sahoo

摘要:

我们利用KEKB非对称能量e+e对撞机上Belle探测器在Y(4S)共振处收集的772 × 10^6个BBar对的数据样本,首次观测到了辐射衰变B^0-> BK^0 γ。我们观察到35+/-8个事件的信号,其显著性为5.4个标准差,包括系统不确定性。测得的分支分数是${\cal B}(B^0->ϕK^0γ) = (2.66\pm 0.60 \pm 0.32) \times 10^{-6}$,其中的不确定性分别是统计和系统的。我们还报告了第一次测量的时间相关的CP破坏参数:${\mathcal S}_{ϕK_S^0 γ} = +0.74^{+0.72}_{-1.05} (stat)^{+0.10}_{-0.24} (syst)$和${\mathcal A}_{ϕK_S^0 γ} = +0.35 \pm 0.58 (stat)^{+0.23}_{-0.10} (syst)$。我们还精确测量了${\mathcal B}(B^+->ϕK^+γ) = (2.34\pm 0.29 \pm 0.23) \times 10^{-6}$。观察到的$M_{ϕK}$质谱显着不同于预期的三体相空间衰变。这些结果是初步的。

英文摘要:

We report the first observation of the radiative decay B^0->ϕK^0γusing a data sample of 772x10^6 BBar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We observe a signal of 35+/-8 events with a significance of 5.4 standard deviations including systematic uncertainties. The measured branching fraction is ${\cal B}(B^0->ϕK^0γ) = (2.66\pm 0.60 \pm 0.32) \times 10^{-6}$, where the uncertainties are statistical and systematic, respectively. We also report the first measurement of time-dependent CP violation parameters: ${\mathcal S}_{ϕK_S^0 γ} = +0.74^{+0.72}_{-1.05} (stat)^{+0.10}_{-0.24} (syst)$ and ${\mathcal A}_{ϕK_S^0 γ} = +0.35 \pm 0.58 (stat)^{+0.23}_{-0.10} (syst)$. We also precisely measure ${\mathcal B}(B^+->ϕK^+γ) = (2.34\pm 0.29 \pm 0.23) \times 10^{-6}$. The observed $M_{ϕK}$ mass spectrum differs significantly from that expected in a three-body phase-space decay. These results are preliminary.

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