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arXiv 1702.08309hep-ex
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用ATLAS探测器探测$\sqrt{\mathrm{s}}=8$ TeV上PDMATHAAC碰撞中PDMATHAAB通道单顶夸克产生和衰变的PDMATHAAA顶点结构

Probing the $Wtb$ vertex structure in $t$-channel single-top-quark production and decay in $pp$ collisions at $\sqrt{\mathrm{s}}=8$ TeV with the ATLAS detector

ATLAS Collaboration

摘要:

为了探测$Wtb$的顶点结构,我们从质心能量为8 TeV的质子-质子碰撞中产生的$t$通道单顶夸克事件中测量了顶夸克和$W$ -玻色子极化观测值。该数据集对应于20.2 fb $^{-1}$的积分光度,在大型强子对撞机上用ATLAS探测器记录。选定的事件包含一个孤立的电子或μ子,大的横向动量和正好两个喷流,其中一个被确定为可能包含$b$ -强子。严格的选择要求适用于歧视$t$通道单顶夸克事件的背景。极化观测量提取的角度分布测量相对于自旋量子化轴适当选择的顶夸克和$W$玻色子的不对称性。在部分子水平上进行的不对称性测量,通过校正所观察到的探测器效应和强子化的角分布减去背景的贡献。测量的顶夸克和$W$玻色子的极化值与标准模型的预测一致。对反常耦合$g_{\mathrm{R}}$虚部的限制也由模型无关的测量值设定。

英文摘要:

To probe the $Wtb$ vertex structure, top-quark and $W$-boson polarisation observables are measured from $t$-channel single-top-quark events produced in proton--proton collisions at a centre-of-mass energy of 8 TeV. The dataset corresponds to an integrated luminosity of 20.2 fb$^{-1}$, recorded with the ATLAS detector at the LHC. Selected events contain one isolated electron or muon, large missing transverse momentum and exactly two jets, with one of them identified as likely to contain a $b$-hadron. Stringent selection requirements are applied to discriminate $t$-channel single-top-quark events from background. The polarisation observables are extracted from asymmetries in angular distributions measured with respect to spin quantisation axes appropriately chosen for the top quark and the $W$ boson. The asymmetry measurements are performed at parton level by correcting the observed angular distributions for detector effects and hadronisation after subtracting the background contributions. The measured top-quark and $W$-boson polarisation values are in agreement with the Standard Model predictions. Limits on the imaginary part of the anomalous coupling $g_{\mathrm{R}}$ are also set from model-independent measurements.

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