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arXiv 1702.06164hep-ex
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sqrt(s)= 13 TeV质子-质子碰撞中四个顶夸克的标准模型产生

Search for standard model production of four top quarks in proton-proton collisions at sqrt(s) = 13 TeV

CMS Collaboration

摘要:

本文报道了在sqrt(s)= 13 TeV的CMS实验中记录的质子-质子碰撞中寻找包含四个顶夸克(ttbar-ttbar)的事件,对应的积分亮度为2.6毫微微垒。分析考虑了单轻子(e或mu)+喷注和相反符号的双轻子(mu+mu-,mu+/- e-/+,或e+e-)+喷注通道。它使用提升决策树来结合全球事件和喷气机属性的信息,以区分ttbar-ttbar和ttbar生产。在所有选择要求后观察到的事件数量与背景和标准模型信号预测的预期一致,并且在标准模型中的ttbar-ttbar产生的横截面上设定上限为94 fb,置信水平为95%(预测值的10.2倍),预期限值为118 fb。这与在同号双轻子通道中发表的CMS搜索结果相结合,在95%的置信水平下得到69 fb的改进极限(预测的7.4倍),预期极限为71 fb。这些是迄今为止对ttbar-ttbar生产速度的最大限制。

英文摘要:

A search for events containing four top quarks (ttbar-ttbar) is reported from proton-proton collisions recorded by the CMS experiment at sqrt(s) = 13 TeV and corresponding to an integrated luminosity of 2.6 inverse femtobarns. The analysis considers the single-lepton (e or mu)+jets and the opposite-sign dilepton (mu+mu-, mu+/- e-/+, or e+e-)+jets channels. It uses boosted decision trees to combine information on the global event and jet properties to distinguish between ttbar-ttbar and ttbar production. The number of events observed after all selection requirements is consistent with expectations from background and standard model signal predictions, and an upper limit is set on the cross section for ttbar-ttbar production in the standard model of 94 fb at 95% confidence level (10.2 times the prediction), with an expected limit of 118 fb. This is combined with the results from the published CMS search in the same-sign dilepton channel, resulting in an improved limit of 69 fb at 95% confidence level (7.4 times the prediction), with an expected limit of 71 fb. These are the strongest constraints on the rate of ttbar-ttbar production to date.

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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