Resonant Few-Body Systems from the Lattice

据我们所知，强力是物质形成的原因，但这种现象如何发生的确切机制仍然是一个谜。强力将原子核中的核子束缚在一起，但它们也导致在更高能量下出现共振现象，例如，在托马斯杰斐逊国家加速器设施（JLab）。对共振的实验和理论探索，以理解强作用力集中在少体系统及其动力学上。这个项目的目的是缩小理论计算之间的差距的少体系统，称为晶格QCD，和唯象学。在这个提议中解决的主要技术挑战涉及的问题，这些计算是在一个小的立方体积，而不是无限的空间，以及如何消除相应的文物，使格点QCD可以比较自然。这些预测与测量的偏差是新物理学的线索。该项目还旨在从概念上改进三体实验数据的分析。 PI将同时开发简单量子力学系统的模拟，以说明本科生和研究生课程沿着标准教科书的路线，以帮助培养多样化的，具有全球竞争力的STEM劳动力。强作用力的理论基础，量子色动力学（QCD），可以使用格点QCD计算。然而，有限体积效应的情况下，三个粒子知之甚少。该项目旨在进一步发展三体方法，使格点QCD结果能够外推到物理世界，并帮助回答有关激发介子和重子性质的QCD预测的基本问题。为此，与核反应中概率守恒有关的么正性原理可以有效地用作指导原则，并且可以扩展到三个或更多粒子的扇区。在这个项目中，方法将在概念上升级，以适用于象征性的共鸣。为了突出一点，罗珀共振已经被研究了几十年，因为它的质量异常轻，而且它作为核子或强子分子的径向激发的性质是有争议的。而且在从头算格点QCD计算中也没有明确的信号。本计画的重点是量化有限体积效应，以解决这个难题。其他研究方向涉及轴向共振，在其三体动力学中，类似于假想的奇异介子--一种在JLab和其他实验中寻找的新型粒子。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Strong forces are responsible for the formation of matter as we know it, but the precise mechanism of how this occurs remain a mystery. Strong forces bind nucleons together in atomic nuclei, but they also lead to the emergence of resonant phenomena at higher energies that are studied, e.g., at the Thomas Jefferson National Accelerator Facility (JLab). The experimental and theoretical quest for resonances to understand the strong force focuses on few-body systems and their dynamics. This project aims at closing the gap between theoretical calculations on few-body systems, called lattice QCD, and phenomenology. The main technical challenge addressed in this proposal concerns the problem that these calculations are performed in a small cubic volume instead of infinite space, and how to remove the corresponding artifacts so that lattice QCD can be compared to Nature. Deviations of these predictions from measurements are hints for new physics. The project also aims to conceptually improve the analysis of three-body data from experiment. The PI will in parallel develop simulations of simple quantum mechanical systems to illustrate the undergraduate and graduate curriculum along the lines of standard textbooks to help develop a diverse, globally competitive STEM workforce.The theory underlying the strong force, Quantum Chromodynamics (QCD), can be calculated using Lattice QCD. However, finite-volume effects for the case of three particles are poorly understood. This project aims to further develop three-body methods to enable the extrapolation of Lattice QCD results to the physical world and to help answer fundamental questions regarding QCD predictions for the properties of excited mesons and baryons. For this, the principle of unitarity, related to the conservation of probability in nuclear reactions, can be efficiently used as the guiding principle, and can be extended to the three- or more particle sector. In this project, methods will be conceptually upgraded to be applied to emblematic resonances. To highlight one, the Roper resonance has been under investigation for decades due to its unusually light mass and its debated nature as radial excitation of the nucleon or hadronic molecule. Furthermore, there is no clear signal for it in ab-initio lattice QCD calculations. The focus of this project is to quantify the finite-volume effects to solve this puzzle. Other lines of investigation address axial resonances that, in their three-body dynamics, resemble the supposed exotic mesons – a new type of particle sought for at JLab and other experiments.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.