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arXiv 1008.0104hep-ex
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B+ --> tau+ nu_tau衰变的强子B标记证据

Evidence for B+ --> tau+ nu_tau decays using hadronic B tags

The BABAR Collaboration, P. del Amo Sanchez

摘要:

我们利用SLAC PEP-II B工厂的BABAR探测器在Upplane(4S)共振处收集的467.8 x 10^6 B-棒对,对B+ --> tau+ nu_tau衰变进行了搜索。我们选择了一个样本的事件与一个完全重建的B-在强子衰变模式(B-> D{(*)0}X-和B-> J/psi X-)。我们检查事件的其余部分以寻找B+ --> tau+ nu_tau衰变。我们在下列模式中识别tau+轻子:tau+ --> e+ nu nu,tau+ --> mu+ nu nu,tau+ --> pi+ nu和tau+ --> rho nu。我们发现相对于预期背景的事件过多,其排除了3.3 sigma水平的零信号假设,并且可以转换为B(B+ --> tau+ nu_tau)=(1.80 + 0.57 - 0.54(stat.)+-0.26(系统))x 10^{-4}。

英文摘要:

We present a search for the decay B+ --> tau+ nu_tau using 467.8 x 10^6 B B-bar pairs collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We select a sample of events with one completely reconstructed B- in an hadronic decay mode (B- --> D{(*)0}X- and B- --> J/psi X-). We examine the rest of the event to search for a B+ --> tau+ nu_tau decay. We identify the tau+ lepton in the following modes: tau+ --> e+ nu nu, tau+ --> mu+ nu nu, tau+ --> pi+ nu and tau+ --> rho nu. We find an excess of events with respect to expected background, which excludes the null signal hypothesis at the level of 3.3 sigma and can be converted to a branching fraction central value of B( B+ --> tau+ nu_tau )=( 1.80 +0.57 -0.54 (stat.) +-0.26 (syst.)) x 10^{-4}.

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