Probing polarised production of two same-charge W bosons produced in association with two jets with the ATLAS detector

Luka Nedic将在他的论文中使用欧洲核子研究中心（瑞士日内瓦）大型强子对撞机（LHC）的ATLAS探测器收集的数据。ATLAS合作涉及来自约40个国家数百个研究所的4000多名科学家、工程师和学生。他的论文将重点研究通过矢量玻色子散射（VBS）产生与射流相关的两个具有相同电荷的W玻色子（ssWWjj）。了解2018年首次观察到的这一过程，特别是与两个喷流（ssWWjj(LL)，预计占ssWWjj事件的5-7%）相关的两个纵向极化W玻色子的产生，是对标准模型和电弱对称性破断机制的关键测试。Luka Nedic将开发新的方法来提取小的ssWWjj信号，提高微分截面测量的精度。使用机器学习工具进行分类和回归，他将探测生产ssWWjj（LL）并执行极化分数的首次测量。他还将致力于通过首次探测强子衰变W玻色子来扩展分析的范围，进一步提高分析的灵敏度。Luka Nedic还将参与ATLAS联合性能组的工作，为LHC第二期的准备工作做出贡献，以更新离线软件，为ATLAS内部跟踪器（ITk）升级的操作做准备。这项任务的完成将使他获得ATLAS作者的资格。

Luka Nedic will use the data collected with the ATLAS detector at the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland) for his thesis. The ATLAS collaboration involves more than 4000 scientists, engineers, and students from hundreds of institutes in about 40 countries. His thesis will focus on studies of the production of two W bosons with the same charge in association with jets (ssWWjj) via vector boson scattering (VBS). Understanding this process first observed in 2018, and in particular the production of two longitudinally polarised W bosons in association with two jets (ssWWjj(LL), expected to be 5-7% of ssWWjj events), is a key test of the Standard Model and the mechanism of Electroweak Symmetry breaking. Luka Nedic will develop new methods to extract the small ssWWjj signal and increase the precision of differential cross-section measurements. Using machine learning tools for classification and regression, he will probe the production ssWWjj(LL) and perform first measurements of the polarisation fraction. He will also work towards extending the reach of the analysis by probing hadronically-decaying W bosons for the first time, further improving the sensitivity of the analysis. Luka Nedic will also contribute to the preparation of LHC Phase-II by participating in the effort conducted in the ATLAS Combined Performance group to update the offline software in preparation of the operation of the ATLAS Inner Tracker (ITk) upgrade. The completion of this task will lead to his qualification as an ATLAS author.