Search for production of a single top quark in association with a Z boson in Standard Model and New Physics scenarios using CMS Run 2 data.

该项目将对CERN LHC的CMS探测器收集的完整运行2数据集进行分析。这些数据将被用来寻找在双轻子末态中与Z玻色子相关的单个顶夸克的产生。这是一个罕见的标准模型（SM）过程，最近首次被观察到，但仅在三轻子末态。除了揭示过程本身以及顶部如何耦合到Z玻色子之外，它对WWZ耦合也很敏感。到目前为止，还没有尝试在双轻子末态进行相应的观测/测量，这从分析的角度来看更具挑战性，但也提供了一个重要的三轻子结果的独立交叉检查，并有可能产生更灵敏的组合结果。需要完整的运行2数据集，以便有任何前景使用此特定最终状态进行观察。分析也将使用新的CMS分析技术和工具进行，与Brunel在该领域所做的先前工作形成对比。除了寻找SM过程之外，运行2数据的相同（或至少密切相关）子集可用于搜索风味变化中性电流（FCNC）tZ生产。在这方面有两个独立的衰变过程可以研究：一个是寻找tZ产生，其中FCNC顶点是产生机制的一部分，可能揭示tZq和tgq异常耦合。另一个是使用包含顶夸克对的事件来搜索tZ产生，其中FCNC顶点发生在其中一个顶夸克的随后衰变中。尽管上述分析将是本项目的主要重点，但预计还将开展维护和运行当前CMS跟踪器的工作，参与运行3数据采集的准备工作。

This project is to work on the analysis of the full Run 2 dataset collected by the CMS detector at the CERN-LHC. The data will be used to search for the production of a single top quark in association with a Z boson in the dilepton final state. This is a rare standard model (SM) process that has recently been observed for the first time, but only in the trilepton final state. In addition to shedding light on the process itself and how the top couples to Z bosons, it is also sensitive to the WWZ coupling.Thus far, there has been no attempt to make the corresponding observation/measurement in the dilepton final state, which is more challenging from an analysis perspective, but also offers an important independent cross-check of the trilepton result and the potential to produce a more sensitive combined result. The full Run 2 dataset will be required for there to be any prospect of making an observation using this particular final state. The analysis will also be done using new CMS analysis techniques and tools, in contrast to the preceding work done in this area at Brunel.In addition to looking for the SM process, the same (or at least a closely-related) subset of the Run 2 data can be used to search for flavour-changing neutral current (FCNC) tZ production. There are two separate decay processes that can be studied in this regard: One is the search for tZ production, where the FCNC vertex is part of the production mechanism, potentially shedding light on both tZq and tgq anomalous couplings. The other is the search for tZ production using events containing a top-quark pair, where the FCNC vertex occurs in the subsequent decay of one of the top quarks. This also has the potential to shed light on the tZq anomalous coupling.Although the analyses described above will be the primary focus of this project, it is expected that there will also be work done on the maintenance and operation of the current CMS Tracker, participating in preparations for Run 3 data-taking.