arXiv 1802.056432018-02-15hep-ex

$\rm t\bar{t}$ +X在CMS上的研究

Studies of $\rm t\bar{t}$+X at CMS

Illia Khvastunov

备注：: 6 pages, 5 figures, proceedings for the fifth annual conference on Large Hadron Collider Physics , Shanghai, Chine, May 15-20, 2017

摘要：

这个演讲致力于最新的测量过程，其特征是顶夸克对的产生，无论是与电弱标准模型玻色子，还是另一对顶夸克，底夸克或轻夸克。对于顶夸克对与光子结合的产生截面的测量，使用CMS探测器在$\sqrt{s}$ = 8 TeV下收集的19.7 $\rm fb^{-1}$的质子-质子碰撞数据，而对于四个顶夸克对产生，$\rm t\bar{t}$ + bb，$\rm t\bar{t}$ + jj，$\rm t\bar{t}$ W和$\rm t\bar{t}$ Z，使用在$\sqrt{s}$ = 13 TeV下收集的总计35.9 $\rm fb^{-1}$的数据。$\rm t\bar{t}γ$的测量是在顶夸克对半轻子衰变链对应的基准相空间中进行的，其截面是相对于包含的顶夸克对产生截面进行测量的。发现该过程的基准横截面为127 $\pm$ 27（stat + syst）fb。最近对四个顶夸克产生的研究，探索了同号双轻子的终态，将观测到的（预期的）上限设定为标准模型截面预测值的4.6（$2.9^{+1.4}_{-0.9}$）倍。在全相空间中，两个b夸克的顶对产生截面为$σ$（$\rm t\bar{t}$ + bb）= 3.9 $\pm$ 0.6（stat）$\pm$ 1.3（syst）pb.对$\rm t\bar{t}$ W和$\rm t\bar{t}$ Z过程的测量结合了三个末态和两个同号、三个和四个轻子。$\rm t\bar{t}$ W和$\rm t\bar{t}$ Z产生横截面的测量结果为$σ$（$\rm t\bar{t}$ Z）= $\rm 1.00^{+0.09}_{-0.08} (stat.)^{+0.12}_{-0.10} (sys.)$ pb和$σ$（$\rm t\bar{t}$ W）= $\rm 0.80^{+0.12}_{-0.11} (stat.)^{+0.13}_{-0.12} (sys.)$ pb，与仅背景假设的预期（观察）显著性分别为4.6（5.5）和9.5（9.9）标准差。

英文摘要：

This talk is dedicated to the most recent measurements of the processes that feature the production of a top quark pair either with an electroweak standard model boson, or another pair of top, bottom or light quarks. For the measurement of the production cross-section of top quark pair in association with a photon, 19.7 $\rm fb^{-1}$ of proton-proton collision data collected by CMS detector at $\sqrt{s}$ = 8 TeV is used, while for four top production, $\rm t\bar{t}$ + bb, $\rm t\bar{t}$ + jj, $\rm t\bar{t}$W and $\rm t\bar{t}$Z the data collected at $\sqrt{s}$ = 13 TeV amounting to 35.9 $\rm fb^{-1}$, is used. The measurement of $\rm t\bar{t}γ$ is performed in the fiducial phase space corresponding to the semileptonic decay chain of the top quark pair, and the cross section is measured relative to the inclusive top quark pair production cross section. The fiducial cross section for this process is found to be 127 $\pm$ 27 (stat + syst) fb. The most recent search for the four top quark production, that explores the same-sign dilepton final state, set the upper observed (expected) limit to 4.6 ($2.9^{+1.4}_{-0.9}$) times predicted standard model cross section. The measured cross section of the top pair production with two b quarks is found to be $σ$($\rm t\bar{t}$ + bb) = 3.9 $\pm$ 0.6 (stat) $\pm$ 1.3 (syst) pb in the full phase space. The measurement of the $\rm t\bar{t}$W and $\rm t\bar{t}$Z processes combines three final states with two same-sign, three and four leptons. The $\rm t\bar{t}$W and $\rm t\bar{t}$Z production cross sections are measured to be $σ$($\rm t\bar{t}$Z) = $\rm 1.00^{+0.09}_{-0.08} (stat.)^{+0.12}_{-0.10} (sys.)$ pb and $σ$($\rm t\bar{t}$W) = $\rm 0.80^{+0.12}_{-0.11} (stat.)^{+0.13}_{-0.12} (sys.)$ pb with an expected (observed) significance of 4.6 (5.5) and 9.5 (9.9) standard deviations from the background-only hypothesis.

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。

摘要：

英文摘要：

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