利用ATLAS探测器在√s=13TeV的质子-质子碰撞中测量tZq的包含及微分截面
Measurement of $tZq$ inclusive and differential cross-sections in $pp$ collisions at $\sqrt{s} = 13~\text{TeV}$ with the ATLAS detector
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中文总结 AI 辅助
本研究利用ATLAS探测器13TeV质子-质子碰撞数据，测量tZq的包含与微分截面等，结果符合标准模型，还对顶夸克相关六维算子设定了限制。
中文摘要 AI 辅助
在三轻子道中测量了顶夸克伴随Z玻色子的t道产生过程tZq，所测量的pp→tℓ⁺ℓ⁻q过程定义为m_{ℓℓ}>30GeV，包含共振Z玻色子产生和非共振双轻子产生。使用ATLAS实验在2015至2018年质心系能量√s=13TeV的质子-质子碰撞中采集的数据，对应积分亮度为140fb⁻¹，筛选出包含三个轻轻子（电子或μ子）、2至4个喷注（其中1或2个被识别为b夸克引发的喷注）的事例。测量了m_{ℓℓ}>30GeV的pp→tℓℓq包含截面，以及顶夸克、顶反夸克产生的单独截面及其比值；该包含截面测量值为95.2⁺⁸.⁵₋₇.₉（统计）⁺⁵.⁵₋₅.₃（系统）fb，与最先进的标准模型预测一致。还给出了多个运动学变量的微分截面测量结果，在粒子层面和部分子层面的各自相空间中分别进行了绝对和归一化微分截面测量。通过顶夸克极化角的展开测量得到顶夸克自旋不对称度A=0.34±0.14（统计）±0.06（系统），与标准模型预测吻合良好。微分截面测量结果在标准模型有效场论框架下进行解释，并对涉及顶夸克的六维算子设定了限制。
英文摘要
The $t$-channel production of a top quark in association with a $Z$ boson, $tZq$, is measured in the trilepton channel. The measured $pp \rightarrow t\ell^+\ell^-q$ process is defined for $m_{\ell\ell} > 30\,\text{GeV}$ and includes both resonant $Z$-boson production and non-resonant dilepton production. The data collected by the ATLAS experiment in 2015 to 2018 in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 13\,\text{TeV}$ are used, corresponding to an integrated luminosity of $140\,\text{fb}^{-1}$. Events containing three light leptons ($e$ or $μ$) and two to four jets, one or two of which are identified as $b$-quark-initiated jets, are selected. The inclusive $pp \rightarrow t \ell\ell q$ cross-section with $m_{\ell\ell} > 30\,\text{GeV}$ is measured, along with the separate cross-sections for top-quark and top-antiquark production and their ratio. The inclusive cross-section is measured to be $95.2\;^{+8.5}_{-7.9}\;\text{(stat.)}\;^{+5.5}_{-5.3}\;\text{(syst.)}\,\text{fb}$ and found to be in agreement with the most advanced Standard Model predictions. Differential cross-section measurements as a function of many kinematic variables are also presented. Both absolute and normalised differential cross-section measurements are made at particle level and parton level in their respective phase spaces. The top-quark spin asymmetry is measured from the unfolded measurement of the top-quark polarisation angle as $A = 0.34 \pm 0.14 \;\text{(stat.)} \pm 0.06\;\text{(syst.)}$, in good agreement with the Standard Model prediction. The differential cross-section measurement results are interpreted in the framework of Standard Model effective field theory and limits are set on dimension-6 operators involving the top quark.
