Searching for Exclusive W decays in ttbar events using the ATLAS detector at the Large Hadron Collider

标准模型预测了W玻色子的唯一强子衰变，但从未被观测到。根据衰变模式，预期的分支分数可能高达百万分之一。该项目旨在利用大型强子对撞机运行2中超过1亿个顶夸克对产生事件的大样本来搜索这种衰变，以及运行3中新的类似大小的数据集。每一个顶夸克衰变为一个底夸克和W玻色子。唯一的W衰变事件可以通过要求一个W玻色子衰变为带电轻子和中微子，然后研究另一个W玻色子的衰变来寻找。具体选择哪种衰变模式将在博士论文中确定，但初始候选衰变是：i）W+-> rho_0 + pi+/rho+，ii）W+-> D_s + γ，iii）W-+> D_0 pi+/rho+，iv）W+ -> D_s + J/Psi。除了分析ttbar数据集外，还计划研究和开发直接W生产中专属衰变的专用触发器，作为本博士学位的一部分。项目如果成功部署，与顶夸克对生产数据集相比，这些可能会将W玻色子的可搜索样本提高两个数量级。

Exclusive hadronic decays of the W-boson are predicted by the Standard Model but have never been observed. Depending on the decay mode, the expected branching fractions could be as high as 1 per million. This project aims to exploit the large sample of > 100 million top-quark-pair production events available from Run 2 of the LHC to search for such decays, as well as new similarly sized datasets from Run 3. Each top quark decays to a bottom quark and W-boson. Exclusive W decay events can then be searched for by requiring that one W Boson decays to a charged lepton and neutrino and then studying the decay of the other W boson. The precise selection of which decay modes to study will be determined during the Ph.D, but initial candidate decays are: i) W+-> rho_0 + pi+/rho+, ii) W+-> D_s + gamma , iii) W-+> D0 pi+/rho+, iv) W+ -> D_s + J/Psi . In addition to analysis of ttbar datasets, it is planned to study and develop dedicated triggers for exclusive decays in direct W production as part of this Ph.D. project. If successfully deployed these could potentially enhance the searchable sample of W bosons by two orders of magnitude compared to the top-quark pair production dataset.