Studying Quantum Chromodynamics at LHCb

日常物质原子核中的质子和中子是由称为夸克和胶子的亚核粒子构成的。该奖项支持的项目将研究从质子中散射出来的夸克和胶子或在高能粒子碰撞中产生的夸克和胶子随后如何形成新的束缚态。额外的测量将研究强核电荷（称为颜色）如何在质子-质子散射过程中流动，寻找理论上预测的夸克和胶子的新状态，这些状态在质子碰撞中表现出量子相关性。来自欧洲核子研究组织（CERN）大型强子对撞机的数据将被用于进行这项研究，作为大型强子对撞机美容（LHCb）实验的一部分。所进行的研究将促进我们对强力束缚态（如质子）是如何产生的，以及它们可能相互作用的动力学的理解。该奖项支持的项目将进一步培养来自不同背景的核物理青年科学家。培训下一代核物理学家对于保持与国家能源和国防需求相关的专业知识以及继续推进核物理和技术的应用和非应用研究至关重要。具体而言，该奖项将支持一名博士后学者和五名博士生在核物理学方面进行LHCb实验的指导研究，其中一名是拉丁美洲人，另一名是非洲裔美国人。第二年，一名来自芒特霍利奥克学院（Mount Holyoke College）的女生将在密歇根大学（University of Michigan）进行暑期核物理研究。PI的小组将通过在LHCb上进行一套互补测量来研究高能彩色带电夸克是如何强子化成可观察的彩色中性束缚态的喷雾的。具体来说，测量将比较主要由轻夸克和重夸克发起的射流中的带电强子分布，包括对夸克质量对强子产生的预测抑制的研究；通过测量重子和介子的产生作为事件多重性的函数来检验强子化的弦断裂和夸克聚结模型的贡献；并通过测量产生的超子的自发极化来研究强子化过程中的自旋动量关系。提出的强子化计划将有助于实现最终的、长期的目标，即能够统计地预测来自不同风味高能碎片夸克的粒子的完全相关分布。单独的测量将探索颜色流在强子散射过程中的作用，通过寻找横向动量依赖的分解破缺和颜色纠缠的实验证据。具体的观测结果包括几乎背靠背的Z玻色子-强子和Z玻色子-射流对的相关产生。此外，这些活动还包括对LHCb上游跟踪硅探测器的调试和优化，以及将其集成到LHCb实时分析框架中。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 protons and neutrons in the atomic nuclei of everyday matter are made of subnuclear particles called quarks and gluons. The project supported by this award will study how quarks and gluons scattered out of a proton or produced in high-energy particle collisions subsequently form new bound states. Additional measurements will investigate how strong nuclear charge, called color, flows through proton-proton scattering processes, searching for a theoretically predicted novel state of quarks and gluons that exhibit quantum correlations across colliding protons. Data from the Large Hadron Collider at the European Organization for Nuclear Research (CERN) will be used to perform the research, as part of the Large Hadron Collider Beauty (LHCb) experiment. The research performed will advance our understanding of how strong force bound states such as protons can be created, and the dynamics of their possible interactions. The project supported by this award will furthermore train young scientists from diverse backgrounds in nuclear physics. Training the next generation of nuclear physicists is critical to maintain expertise relevant to the nation's energy and defense needs and to continue advancing both applied and non-applied research in nuclear physics and technology. Specifically, this award will enable mentored research in nuclear physics on the LHCb experiment by a postdoctoral scholar and five Ph.D. students, including one who is Latina American and another who is African American. In the second year, a student from Mount Holyoke College, an undergraduate institution for women, will perform summer research in nuclear physics at the University of Michigan.The PI’s group will study how high-energy color-charged quarks hadronize into sprays of observable color-neutral bound states by performing a suite of complementary measurements at LHCb. Specifically, the measurements will compare charged hadron distributions in jets initiated predominantly by light versus heavy quarks, including investigation of the predicted suppression of hadron production with the mass of the quark; examine evidence for contributions from string breaking versus quark coalescence models of hadronization via measurements of baryon versus meson production as a function of event multiplicity; and study spin-momentum correlations in hadronization by measurement of spontaneous polarization of produced hyperons. The proposed hadronization program will contribute toward the ultimate, long-term goal of being able to predict statistically the fully correlated distributions of particles from different flavor high-energy fragmenting quarks. Separate measurements will explore the role of color flow in hadronic scattering processes by searching for experimental evidence of transverse-momentum-dependent factorization breaking and color entanglement. The specific observables include correlated production of nearly back-to-back Z boson-hadron and Z boson-jet pairs. The activities furthermore include contributions to the commissioning and optimization of the U.S.-led Upstream Tracker silicon detector upgrade for LHCb as well as its integration into the LHCb real-time-analysis framework.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.