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arXiv 0705.2966hep-ex
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在CDF上测量顶夸克衰变中的W玻色子螺旋度分数

Measurement of the W-boson helicity fractions in top-quark decays at CDF

Thorsten Chwalek

摘要:

本文用CDF Ⅱ探测器测量了顶夸克衰变中纵向极化右手W玻色子的分数F_0和F_+。分析中使用的数据集对应于约955 pb-1的积分亮度。我们选择一个轻子,至少四个喷流,和失踪的横向能量的顶-反顶候选事件。我们的螺旋度测量使用衰变角θ *,它被定义为W玻色子静止框架中带电轻子的动量与顶夸克静止框架中的W动量之间的角度。数据中的cos(theta*)分布由顶部-自顶候选物的完全运动学重建来确定。我们发现F_0 = 0.59 +- 0.12(stat)+0.07 -0.06(syst)和F_+ = -0.03 +- 0.06(stat)+0.04 -0.03(syst),这与标准模型的预测是一致的。在95%的置信水平上,我们对F_+ < 0.1的右手W玻色子的分数设定了上限。

英文摘要:

We present a measurement of the fractions F_0 and F_+ of longitudinally polarized and right-handed W bosons in top-quark decays using data collected with the CDF II detector. The data set used in the analysis corresponds to an integrated luminosity of approximately 955 pb-1. We select top-antitop candidate events with one lepton, at least four jets, and missing transverse energy. Our helicity measurement uses the decay angle theta*, which is defined as the angle between the momentum of the charged lepton in the W boson rest-frame and the W momentum in the top-quark rest-frame. The cos(theta*) distribution in the data is determined by full kinematic reconstruction of the top-antotop candidates. We find F_0 = 0.59 +- 0.12 (stat) +0.07 -0.06 (syst) and F_+ = -0.03 +- 0.06 (stat) +0.04 -0.03 (syst), which is consistent with the standard model prediction. We set an upper limit on the fraction of right-handed W-bosons of F_+ < 0.1 at the 95% confidence level.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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