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arXiv 0704.3063hep-ex
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反演(1 S)到eta和eta'的辐射衰变的研究

Search for Radiative Decays of Upsilon(1S) into eta and eta'

S. B. Athar, CLEO Collaboration

摘要:

我们报告了在康奈尔电子储存环(CESR)上用CLEO III探测器收集的21.2 +/- 0.2 × 10^6的Uppersons(1 S)衰变中寻找Uppersons(1 S)到赝标介子eta和etaprime的辐射衰变。η介子在三种模式下重建,η到γ-γ,η到pi+ pi-pi 0和η到3 pi 0。etaprime介子在etaprime到pi+ pi- eta的模式下重建,其中eta通过上述三种模式中的任何一种衰减,并且etaprime到γ rho,其中rho衰减到pi^+ pi^-。七个子模式中的五个被发现几乎是无背景的。在其中的四个中,我们没有发现信号候选者,并且在一个Uppersons(1 S)到gamma-etaprime、etaprime到pi+ pi-eta、eta到pi+ pi-pi 0中,存在两个良好的信号候选者,这不足以证明信号。其他两个子模式eta到gamma-gamma和etaprime到gamma rho是背景限制的,并且在它们的信号区域中没有显示出过量的事件。我们结合不同渠道的结果,并在90% C. L.处获得上限。即B(Upperoxide(1 S)对γ eta)< 1.0 × 10^-6,B(Upperoxide(1 S)对γ etaprime)< 1.9 × 10^-6。我们的极限是一个数量级比以前的紧,低于一些理论模型的预测。

英文摘要:

We report on a search for the radiative decay of Upsilon(1S) to the pseudoscalar mesons eta and etaprime in 21.2 +/- 0.2 times 10^6 Upsilon(1S) decays collected with the CLEO III detector at the Cornell Electron Storage Ring (CESR). The eta meson was reconstructed in the three modes eta to gamma-gamma, eta to pi+pi-pi0 and eta to 3pi0. The etaprime meson was reconstructed in the mode etaprime to pi+ pi- eta with eta decaying through any of the above three modes, and also etaprime to gamma rho, where rho decays to pi^+ pi^-. Five out of the seven sub-modes are found to be virtually background-free. In four of them we find no signal candidates and in one Upsilon(1S) to gamma-etaprime, etaprime to pi+ pi- eta, eta to pi+pi-pi0 there are two good signal candidates, which is insufficient evidence to claim a signal. The other two sub-modes eta to gamma-gamma and etaprime to gamma rho are background limited, and show no excess of events in their signal regions. We combine the results from different channels and obtain upper limits at the 90% C.L. which are B(Upsilon(1S) to gamma eta) < 1.0 times 10^-6 and B(Upsilon(1S) to gamma etaprime) < 1.9 times 10^-6. Our limits are an order of magnitude tighter than the previous ones and below the predictions made by some theoretical models.

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