Unifying the Diquark and Molecular Models for Exotic Hadrons

强大的核力负责将质子和中子聚集到原子核的微小空间中，也是将基本的“夸克”粒子结合成称为“强子”的化合物的驱动力。在夸克模型发展后的50年里，人们只知道两种类型的强子：3夸克的“重子”（包括质子和中子）和1夸克/1反夸克的“介子”。然而，自2003年以来，已经发现了50个明显属于“四夸克”或“五夸克”的新粒子，而且每年都有更多的粒子被发现。然而，它们的内部结构，影响它们的外部特性，甚至影响它们的数量，仍然没有解决。这种结构的两种最突出的模型是将新粒子视为已知强子的分子，或将其视为“双夸克”的束缚态。在NSF之前的资助下，PI开发了后者的一个变体，即“动态双夸克模型”，该模型在解释数据方面特别成功，并且包括博士和本科生参与研究。在新的资助下，PI将展示（再次，与初级同事）如何通过包括分子模型特别好地包含的物理效应来推广模型。这项工作将为这些新型粒子提供现存的最好的统一模型。21世纪发现的几乎所有粒子要么是填补夸克模型空白的传统重夸克强子，要么是可能是四夸克或五夸克的外来强子。迄今为止观测到的50个外来物种中，对它们的光谱或结构还没有达成共识。最著名的替代方案是双强子分子和双夸克准粒子的束缚态。PI最近通过Born-Oppenheimer（绝热）近似建立了一个完全基于双夸克相互作用的奇异体模型，并获得了由现有测量支持的多个定量结果，其程度令人惊讶。然而，许多外来物种与双强子阈值的显著接近表明，它们也有很强的分子成分。包括双夸克和分子成分相当于处理绝热公式中的水平交叉。PI将把原子物理的非绝热混合形式应用于双夸克基奇异强子态的混合，其振幅增强发生在双强子阈值附近（分子模型的主要特征），并获得对奇异子的光谱和衰变特性的详细预测，从而创建迄今为止物理上最真实的奇异子模型。这种方法很容易实现，正如PI最近的出版物所展示的那样，博士生和高年级本科生都可以使用。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 strong nuclear force, responsible for packing protons and neutrons together into the tiny space of the atomic nucleus, is also the driving force that combines fundamental “quark” particles into compounds called “hadrons”. For 50 years after the development of the quark model, only two types of hadrons were known: 3-quark “baryons” (including protons and neutrons) and 1-quark/1-antiquark “mesons”. Since 2003, however, 50 new particles have been discovered that are apparent “tetraquarks” or “pentaquarks”, and more are being found every year. Nevertheless, their internal structure, which influences their external properties and even how many there are, remains unresolved. The two most prominent models for this structure are to treat the new particles either as molecules of known hadrons, or as bound states of “diquarks”. Under previous NSF funding, the PI developed a variant of the latter, the “dynamical diquark model”, that has been particularly successful in explaining data, and included PhD and undergraduate students in the research. Under the new grant, the PI will show (again, with junior colleagues) how to generalize the model by including physical effects that molecular models incorporate especially well. This work will produce the best unified model in existence for these new types of particle.Nearly all particles discovered in the 21st century are either conventional heavy-quark hadrons that fill gaps in the quark model, or exotic hadrons that are likely tetraquarks or pentaquarks. Of the 50 exotics observed to date, no consensus has emerged regarding their spectrum or structure. The best-known alternatives are di-hadron molecules and bound states of diquark quasiparticles. The PI recently developed a complete model of exotics based solely upon diquarks interacting via the Born-Oppenheimer (adiabatic) approximation, and obtained multiple quantitative results supported by existing measurements to a surprising degree. However, the remarkable proximity of many exotics to di-hadron thresholds suggests a strong molecular component as well. Including both diquark and molecular components amounts to handling level crossings in a diabatic formulation. The PI will apply the atomic-physics diabatic formalism of configuration mixing to the mixing of diquark-based exotic hadronic states with amplitude enhancements that occur near di-hadron thresholds (a primary feature of molecular models), and obtain detailed predictions for the spectrum and decay properties of exotics, thus creating the most physically realistic model for exotics to date. The approach is straightforward to implement, and as demonstrated by the PI’s recent publications, is accessible to both PhD students and advanced undergraduates.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.