The Higgs boson and the top quark in the ATLAS detector: gateway to new physics

ATLAS 探测器中的希格斯玻色子和顶夸克：通向新物理学的大门

• 批准号: SAPPJ-2020-00034
• 负责人: David, Claire
• 金额: $ 3.64万
• 依托单位: York University
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Project
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=718496
• 关键词: Higgs; boson; top; quark; ATLAS

In the quest to understand the universe through its elementary constituents, CERN's Large Hadron Collider (LHC) has delivered important results confirming the current theory of particle physics, the Standard Model (SM). The discovery of the Higgs boson was a remarkable achievement: it explained how elementary particles acquired their masses. Despite being a very accurate description of the fundamental particle physics laws at the quantum scale, the SM fails to explain major cosmological phenomena in our universe. Finding a sign of “new physics” extending beyond the SM would be a ground-breaking discovery, and a guide toward a more complete description of nature. A promising gateway to probe for signatures of new physics is the measurement of the Higgs boson's interaction with the heaviest particle of matter: the top quark. The interaction strength, called Yukawa coupling, is very sensitive to new physics, and any deviation with respect to the theoretical prediction would uncover non-SM phenomena. I led the effort on the background evaluation towards the observation of the Higgs boson production in association with a top quark pair, or ttH, with the multipurpose ATLAS detector at the LHC. The ttH production mode is the physics process that can give direct access to the top quark Yukawa coupling. However, extracting the ttH signal from the LHC data is extremely challenging; the main background processes are very difficult to accurately model. The simulations, traditionally performed using Monte Carlo (MC) techniques, are intrinsically biased due to theoretical limitations. I propose to deploy advanced machine learning tools to measure with better precision the top quark Yukawa coupling in order to exploit the full potential of the incoming LHC Run 3 (2021 - 2023). Generative Adversarial Networks (GANs) are promising deep learning models with relevant applications in high energy physics. I propose a gradual approach to implement GANs for mitigating the large theoretical uncertainties and make the ttH analysis less reliant on MC simulations. This is in preparation for the High-Luminosity LHC program starting 2026, where the needs of MC with high statistics is almost multiplied by ten. GAN-generated collisions would be faster to produce than MC and much less computationally intensive. Preparing for the High-Luminosity LHC also requires detector upgrades and I propose to use my expertise in particle detector characterization to join the effort of the York University/Toronto cluster, which is in charge of producing and testing 500 sensor units (silicon and electronics) of the future ATLAS inner tracker. York University is best suited to be the dedicated site for detailed evaluation and recovery of components failing standard quality assurance tests. I propose to design and construct the evaluation laboratory, and oversee the reevaluation and recovery efforts during production.

为了通过基本成分来理解宇宙，欧洲核子研究中心的大型强子对撞机（LHC）已经提供了重要的结果，证实了粒子物理学的当前理论，标准模型（SM）。希格斯玻色子的发现是一项了不起的成就：它解释了基本粒子如何获得质量。尽管SM在量子尺度上非常准确地描述了基本粒子物理定律，但它无法解释我们宇宙中的主要宇宙学现象。找到一个延伸到SM之外的“新物理学”的迹象将是一个突破性的发现，也是一个更完整的自然描述的指南。 探测新物理学特征的一个有希望的途径是测量希格斯玻色子与最重的物质粒子：顶夸克的相互作用。被称为汤川耦合的相互作用强度对新物理非常敏感，任何与理论预测的偏差都将揭示非SM现象。我领导了对希格斯玻色子生产的观察与顶夸克对（ttH）的背景评估工作，并在大型强子对撞机上使用多功能ATLAS探测器。ttH产生模是一个直接研究顶夸克汤川耦合的物理过程。然而，从LHC数据中提取ttH信号是非常具有挑战性的;主要的背景过程很难准确建模。传统上使用蒙特卡罗（MC）技术进行的模拟，由于理论上的限制，本质上是有偏见的。 我建议部署先进的机器学习工具来更精确地测量顶夸克汤川耦合，以充分利用即将到来的LHC运行3（2021 - 2023）的潜力。生成对抗网络（GAN）是有前途的深度学习模型，在高能物理中具有相关应用。我提出了一种渐进的方法来实现GAN，以减轻大的理论不确定性，并使ttH分析不那么依赖MC模拟。这是为2026年开始的高亮度LHC计划做准备，届时高统计数据的MC需求几乎是10倍。GAN生成的碰撞将比MC生成得更快，计算密集度也要低得多。 为高亮度LHC做准备还需要升级探测器，我建议利用我在粒子探测器特性方面的专业知识，加入约克大学/多伦多集群的工作，该集群负责生产和测试未来ATLAS内部跟踪器的500个传感器单元（硅和电子器件）。约克大学最适合作为详细评估和恢复未通过标准质量保证测试的组件的专用站点。我建议设计和建造评估实验室，并监督生产过程中的重新评估和恢复工作。