Experimental Study of Heavy Flavor and CP Violation with the LHCb Experiment at the CERN LHC Collider

上个世纪最伟大的科学成就之一是基本粒子、夸克和轻子及其相互作用的标准模型的发展。对标准模型基本元素的精确测试是基本粒子物理学继续研究的最重要目标之一。本项目的重点是重味道的实验研究，它指的是含有魅力(C)夸克和底(B)夸克的粒子，以及CP破坏，即粒子与其反粒子对应粒子性质的差异。这些研究将与欧洲核子研究中心大型强子对撞机上的LHCb实验一起进行，包括对导致物质和反物质性质差异的机制进行精确测试，以及检查带电轻子的普遍行为，轻子是标准模型的基石。味道物理的发现，特别是在标准模型之外发现CP破坏的新来源，也可能对理解宇宙中物质-反物质不对称的起源和宇宙学领域产生深远的影响。实验粒子物理还为培养各级学生以及各种技术前沿的博士后研究人员和工程师提供了极其丰富的环境。马里兰集团在这方面有很好的记录，这得益于LHCb探测器第一次升级的开发，并计划在未来十年继续并加强这一计划，以实现探测器的下一次重大改进计划。拟议的计划包括完成LHCb升级中上游跟踪器的调试，其建造一直是该小组的关键重点，以及主要参与LHCb在运行1和AMP中记录的数据的物理分析；物理研究计划集中在与B介子衰变中的两个电流反常有关的测量上：(1)半轻子B衰变中偏离轻子特征普适性的迹象和(2)B→Kπ衰变家族中CP破坏的研究，其中当前对CP不对称性的测量偏离了基于同位旋对称性的预期模式--长期存在的所谓的“Kπ”谜题。如果得到证实，这些异常现象可能是由于风味过程中存在新的物理效应。该计划还包括主要参与LHCb检测器的下一次重大升级的开发-升级II，预计这将导致香料加工精度的显著提高。在目前的精度水平上，目前与标准模型预测基本一致的关键香料可观测值的测量对新物理模型的能量规模和结构施加了严格的限制。然而，偏离SM的领域正在出现，例如半轻子B衰变中的轻子非普适性的迹象，这些迹象对新标量的存在高度敏感。根据LHCb及其升级的探测器的数据，未来一些关键区域的测量精度预计将达到所需的灵敏度，以澄清其中一些异常或进一步加强与SM预测的偏差。这些结果与能源前沿的研究相结合，可以为超越SM的物理学结构指明方向。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

One of the greatest scientific achievements of the past century has been the development of the Standard Model of elementary particles, the quarks and leptons, and their interactions. The precise tests of the fundamental elements of the Standard Model are among the most important goals of the continuing research in elementary particle physics. This project focuses on an experimental study of heavy flavor, which refers to the studies of the particles containing the charm (c) and the bottom (b) quarks, and CP violation, the differences in the properties of the particles and their antiparticles counterpart. The studies, which will be conducted with the LHCb experiment at the Large Hadron Collider at CERN, include precise tests of the mechanism responsible for the differences in the properties of matter and antimatter as well as examination of the universal behavior of charged leptons, a cornerstone of the Standard Model. The findings of the flavor physics, in particular a potential discovery of new sources of CP violation beyond the Standard Model, will also likely have a profound impact on the understanding of the origin of the matter-antimatter asymmetry in the universe and the field of cosmology. Experimental particle physics also serves as an extremely rich environment for training students at all levels, as well as postdoctoral researchers and engineers at the leading edge of a diverse range of technologies. The Maryland group has had strong record in this area, enabled by the development of the first upgrade of the LHCb detector, and aims to continue and strengthen this program with the next major improvement plan of the detector in the coming decade.The proposed program includes the completion of the commissioning of the upstream tracker in the LHCb upgrade, whose construction has been a key focus of the group, as well as a major participation in the physics analysis of the data recorded by LHCb in Runs 1 & 2 and the anticipated data from the operation of the experiment in the next three years, Run 3. The physics studies program is focused on measurements related to two of the current anomalies in the decays of B mesons: (1) hints of departure from Lepton Flavor Universality in semileptonic B decays and (2) studies of CP violation in the family of B → Kπ decays, where the current measurements of the CP asymmetries deviate from the expected pattern based on isospin symmetry- the long standing so-called ”Kπ” puzzle. These anomalies, if confirmed, could be due to the presence of new physics effects in flavor processes. The program also includes major participation in the development of the next major upgrade of the LHCb detector- Upgrade II, which is expected to lead to significant improvement in the precision of flavor processes. At the current level of precision, measurements of the key flavor observables, currently largely consistent with the Standard Model predictions, impose severe constraints on the energy scale and the structure of new physics models. However, areas of deviations from the SM are emerging, such as signs of lepton non-universality in semileptonic B decays, which are highly sensitive to the presence of new scalars. The precision of future measurements in some key areas, based on the data from LHCb and its upgraded detector, are expected to reach the required sensitivity to clarify some of these anomalies or further strengthen the deviations from the SM predictions. These results could, in conjunction with studies at the energy frontier, point the way to the structure of the physics beyond the SM.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.