论文标题
在顶部夸克和光子之间搜索带有Atlas检测器$ \ sqrt {s} = 13 $ TEV的Quark和Photon之间的中性耦合
Search for flavour-changing neutral-current couplings between the top quark and the photon with the ATLAS detector at $\sqrt{s} = 13$ TeV
论文作者
论文摘要
这封信记录了对改变风味的中性电流（FCNC）的搜索，这些电流在标准模型中被强烈抑制，在带有光子的事件和带有ATLAS探测器的顶部夸克的事件中。该分析使用$ \ sqrt {s} = 13 $ tev在LHC运行2期间收集的数据，对应于139 fb $^{ - 1} $的集成光度。考虑到FCNC顶级生产和衰减。最终状态由一个被带电的Lepton，缺少横向动量，A $ B $标记的喷气机，一个高弹药光子以及可能的其他喷气机组成。多类深神经网络用于将事件分类为两个类别之一的信号，即FCNC产生或衰减或背景。在背景预测上没有明显过量的事件，并且在左手和右手FCNC相互作用的强度上放置了95％CL上限。 FCNC顶部Quark衰变的分支分数上的95％Cl界限是从顶级生产和衰减中估算的，是$ \ Mathcal {b}（t \ rightarrowuγ）<0.85 \ 0.85 \ times 10^{ - 5} $ and $ \ nationcal and $ \ nathcal {b} $ { $TQγ$耦合，以及$ \ Mathcal {b}（t \ toUγ）<1.2 \ times 10^{ - 5} $和$ \ Mathcal {b}（t \ toCγ）<4.5 \ times <4.5 \ times 10^{ - 5} $用于右手耦合。
This letter documents a search for flavour-changing neutral currents (FCNCs), which are strongly suppressed in the Standard Model, in events with a photon and a top quark with the ATLAS detector. The analysis uses data collected in $pp$ collisions at $\sqrt{s} = 13$ TeV during Run 2 of the LHC, corresponding to an integrated luminosity of 139 fb$^{-1}$. Both FCNC top-quark production and decay are considered. The final state consists of a charged lepton, missing transverse momentum, a $b$-tagged jet, one high-momentum photon and possibly additional jets. A multiclass deep neural network is used to classify events either as signal in one of the two categories, FCNC production or decay, or as background. No significant excess of events over the background prediction is observed and 95% CL upper limits are placed on the strength of left- and right-handed FCNC interactions. The 95% CL bounds on the branching fractions for the FCNC top-quark decays, estimated from both top-quark production and decay, are $\mathcal{B}(t\rightarrow uγ) < 0.85 \times 10^{-5}$ and $\mathcal{B}(t\to cγ) < 4.2 \times 10^{-5}$ for a left-handed $tqγ$ coupling, and $\mathcal{B}(t\to uγ) < 1.2 \times 10^{-5}$ and $\mathcal{B}(t\to cγ) < 4.5 \times 10^{-5}$ for a right-handed coupling.
