Probing the Structure of Exotic and Conventional Hadrons

量子色动力学（QCD）是基于夸克和胶子理论的强相互作用的微观理论，它使我们能够理解强子（重子，包括构成原子核的质子和中子，以及介子及其激发）是如何形成的。半个多世纪以来，已知的强子要么属于3-夸克复合物（重子），要么属于夸克-反夸克复合物（介子）。 自2003年以来，已经发现了近36个新的“奇异”强子，它们属于4夸克四夸克和5夸克五夸克的范畴。也就是说，像这些新粒子的多重性和质量之间的间距的原因，以及它们内部的夸克如何排列的问题等基本问题仍然没有解决。 该项目的目标是开发一种物理范式（由PI及其合作者开创），称为动力学双夸克图像，成为一个完全预测的模型，用于计算奇异强子的物理性质。 该模型将在PI指导的研究生的参与下开发。主要项目研究是发展一个预测模型来描述已经（并将继续）在charmonium和bottomonium部门发现的重夸克奇异强子。 即使是关于外来物种的基本问题，比如它们的基本结构，也还没有解决。 最近，PI和他的合作者开发了“动力学”双夸克图像-其中两个夸克（或反夸克）组合称为双夸克的组合迅速彼此分离，但仍然受到QCD色禁闭的约束-作为四夸克态的可能结构。 实现这一图景的完整模型的开发构成了本项目中PI的原理研究。 该模型将使用基于Born-Oppenheimer（B-O）近似的有效场论，部分与其他学术机构的高级研究人员合作开发。 在B-O近似中所需的势能函数的参数可以从晶格数值模拟的结果中收集。 研究出这个模型的所有含义将形成博士学位。一个由PI指导的学生项目。 然后将模型预测的外来物质的质量、衰变模式和内部结构与实验直接进行比较。该奖项反映了NSF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。

Quantum Chromodynamics (QCD)is the microscopic theory of the strong interactions based on the theory of quarks and gluons that allows us to understand how hadrons (baryons, including the protons and neutrons that make up an atomic nucleus, and mesons and their excitations) are formed. For over a half century, the only known hadrons fit into the categories of either 3-quark compounds (baryons) or quark-antiquark compounds (mesons). Since 2003, almost 3 dozen new "exotic" hadrons, fitting into the categories of 4-quark tetraquarks and 5-quark pentaquarks, have been discovered. That said, fundamental questions like the reason for the multiplicity and spacing between masses of these new particles, as well as the question of how the quarks inside them arrange themselves, are still unresolved. The goal of this project is to develop a physical paradigm (pioneered by the PI and his collaborators) called the dynamical diquark picture into a fully predictive model that will be used to compute the physical properties of exotic hadrons. This model will be developed with the participation of a graduate student mentored by the PI. The primary project research is the development of a predictive model to describe the heavy-quark exotic hadrons that have been (and continue to be) discovered in the charmonium and bottomonium sectors. Even fundamental issues about exotics like their basic structure are not yet settled. Recently, the PI and his collaborators developed the "dynamical" diquark picture -- in which combinations of two quark (or antiquark) combinations called diquarks rapidly separate from each other, but are still bound by QCD color confinement -- as a possible structure for tetraquark states. The development of a full model implementing this picture forms the PI's principle research in this project. The model will be developed using an effective field theory based upon the Born-Oppenheimer (B-O) approximation, partly in collaboration with senior researchers at other academic institutions. Parameters for the potential energy functions needed in the B-O approximation can be gleaned from the results of lattice numerical simulations. Working out all the implications of this model will form the Ph.D. project for a student mentored by the PI. The masses, decay modes, and internal structure of exotics predicted by the model will then be compared directly to experiment. Numerous yet-unseen states are likely to be predicted.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.