Physics Beyond Standard Model with the CMS Pixel Detector

粒子物理学的标准模型是一个成功的理论，与几十年来涉及弱、电磁和强相互作用的实验观察相一致。在大型强子对撞机上发现希格斯玻色子进一步证实了这一成功。然而，标准模型仍然是一个不完整的理论。这项研究的重点是在最小尺度上探索宇宙的性质及其基本对称性，目的是了解质量的稳定性、暗物质的量子性质、引力与亚原子力和额外空间维度的关系。该项目以目前在瑞士日内瓦欧洲核子研究中心的大型强子对撞机（LHC）上运行的CMS实验为中心。在大型强子对撞机上对希格斯玻色子性质的精确测量可以让我们深入了解质量的本质和电弱对称性破缺的本质。大型强子对撞机可能会为超对称（一种自然解释电弱对称性破缺的理论）揭示质量较轻的候选者。对“缺失能量”的精确测量可以揭示许多未被发现的粒子的特征，其中一些可能是暗物质的候选者。缺失的能量也可以解释引力子在额外维度或其他奇异粒子中逃逸的原因。本研究的主要重点是利用新安装的CMS像素探测器的能力来追求超对称的搜索。这种新的探测器有一个额外的桶和端盖层，一个减少的材料轮廓，一个新的读出芯片，以尽量减少由于LHC事件的高堆积造成的数据损失，以及一个优化的探测器布局，在整个CMS伪快度范围内覆盖4像素。这些改进转化为更高的跟踪效率，更低的假跟踪率，更低的死区时间/数据丢失，延长探测器的使用寿命，所有这些都导致更好的μ子识别，b-夸克标记，光子/电子识别，tau重建，改进的“粒子流”分析和缺失能量重建。由于改进的b标记和更好的缺失能量估计，提高了信号选择效率，这是该分析程序发现超对称的核心。这项工作还将包括设计和开发额外的像素探测器升级，同时保持对像素探测器操作的支持。构建、调试和维护最先进的硅探测器的挑战为物理和工程领域的劳动力发展提供了机会。该奖项提供的数据分析技术和相关算法、硬件仪器、网格计算和大数据科学机会为学生提供宝贵的经验和知识，使他们能够在学术界或私营部门追求成功的职业生涯。Quarknet外展活动进一步促进了与高中教师的合作，加强了波多黎各学校周围的教学和学习，并激励学生学习STEM学科。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Standard Model of particle physics has been a successful theory, agreeing with decades of experimental observations involving weak, electromagnetic, and strong interactions. The discovery of the Higgs boson at the LHC was further confirmation of this success. However, the Standard Model remains an incomplete theory. This research focuses on probing the nature of the Universe at the smallest scales and its basic symmetries with the goal of understanding the stability of mass, the quantum nature of dark matter, and the relation of gravity to subatomic forces and extra spatial dimensions. This program is centered on the CMS experiment currently running at the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland. The precise measurements of the properties of the Higgs boson at the LHC could give insight into the nature of mass and the nature of electroweak symmetry breaking. The LHC might unveil lighter mass candidates for Supersymmetry, a theory that naturally explains electroweak symmetry breaking. The precise measurement of 'missing energy' could unveil signatures of many undiscovered particles, some of which could be candidates for Dark Matter. Missing energy could also account for the graviton escaping in extra-dimensions or for other exotic particles.The primary focus of this research is to exploit the capabilities of the newly installed CMS pixel detector to pursue searches for Supersymmetry. This new detector has an extra barrel and endcap layers, a reduced material profile, a new readout chip to minimize data losses due to high pile-up of LHC events, and an optimized detector layout for 4-pixel-hit coverage over the full CMS pseudorapidity range. These improvements translate to higher tracking efficiencies, lower fake-track rates, lower dead-time/data-loss, an extended lifetime of the detector, all leading to better muon identification, b-quark tagging, photon/electron identification, tau reconstruction, improved "particle flow" analysis, and missing energy reconstruction. An improved signal selection efficiency due to improved b-tagging and better missing energy estimation is central to this analysis program to discover Supersymmetry. This effort will also include activities in design and development of additional pixel detector upgrades while maintaining support of Pixel Detector Operations. This challenge of building, commissioning, and maintaining a state-of-the-art silicon detector provides workforce development opportunities in physics and engineering. The data analyses techniques and related algorithms, hardware instrumentation, grid computing, and big data science opportunities carried out in this award give students valuable experience and knowledge enabling them to pursue successful careers in academia or the private sector. The Quarknet outreach activities further foster collaboration with high school teachers, strengthening teaching and learning around the schools in Puerto Rico and motivating students to pursue STEM disciplines.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.