Hadron Spectroscopy in the Light Quark Sector at GlueX

GlueX 光夸克领域的强子光谱

• 批准号: SAPPJ-2022-00023
• 负责人: Papandreou, Zisis
• 金额: $ 12.02万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Project
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=762547
• 关键词: Hadron; Spectroscopy; Light; Quark; Sector

Subatomic physics seeks to understand nature - and all its laws - at the most fundamental level, down to its elementary constituents and their interactions. Tremendous strides have been made in the last several decades, using accelerators and astrophysical observations, which have strengthened our conviction that the basic model, known as the Standard Model, is essentially a valid description of the subatomic world but not necessarily a complete one. Among the four forces of the Standard Model, the strong force inside an atomic nucleus is understood by a theory called Quantum Chromodynamics (QCD). QCD describes the physics underlying the interaction of quarks and gluons and it seems to permit a rich spectrum of allowed constituents, whereas nature prefers to reveal a narrower set of quark and gluonic composite states. Features of QCD include six flavors of quarks with various masses, strongly interacting quarks and gluons, and the phenomena of asymptotic freedom and confinement. To date only colourless "quark model" states have been observed - such as quark-antiquark pairs (mesons) and quark triplets (baryons) - while gluonic degrees of freedom are difficult to observe or suppressed. But QCD predicts more types of states than just mesons and baryons. The goal of the GlueX Experiment is to produce and identify unseen exotic forms of matter that exhibit unique signatures among all other particles, which will allow QCD to be tested in a constraining manner. Specifically, hybrid mesons result from the addition of gluon quantum numbers to those of the quarks and a subset of hybrids is predicted to have exotic quantum number combinations that are not allowed in the simple quark model. This is a difficult task requiring experimental conditions that have recently become possible in accelerator and detector technology. GlueX is addressing the former by employing a unique, high-intensity, polarized photon beam and a hermetic detector. The latter has benefited by the recent development of large silicon-based photo sensors that are completely immune to magnetic fields. Our group played a defining role in guiding industry towards their development and these devices are now available commercially to the subatomic, medical and nuclear safety fields. The GlueX plan is to map out the QCD spectrum by systematically studying all decay modes of conventional and hybrid mesons. This effort needs to reconcile state-of-the-art experimental results with state-of-the-art experimental interpretation. The latter is limited by uncertainties in obtaining a robust theoretical description rather than our understanding of the detector or the statistical precision of the data. Our group will pursue the analysis of low-mass mesons, in regions where there is sparse or no real-world data. This research will provide data in controversial (past experiments with low statistical power) as well as unexplored domains of meson spectroscopy.

亚原子物理学试图从最基本的层面理解自然及其所有定律，直至其基本成分及其相互作用。在过去的几十年里，使用加速器和天体物理观测取得了巨大的进步，这增强了我们的信念，即称​​为标准模型的基本模型本质上是对亚原子世界的有效描述，但不一定是完整的描述。在标准模型的四种力中，原子核内部的强力是通过一种称为量子色动力学（QCD）的理论来理解的。 QCD 描述了夸克和胶子相互作用的物理原理，它似乎允许丰富的允许成分谱，而大自然更喜欢揭示一组较窄的夸克和胶子复合态。 QCD 的特征包括六种不同质量的夸克、强相互作用的夸克和胶子，以及渐近自由和禁闭现象。迄今为止，仅观察到无色的“夸克模型”状态 - 例如夸克-反夸克对（介子）和夸克三重态（重子） - 而胶子自由度很难观察或抑制。但 QCD 预测的态类型不仅仅是介子和重子。 GlueX 实验的目标是产生和识别看不见的奇异物质形式，这些物质在所有其他粒子中表现出独特的特征，这将使 QCD 能够以一种约束性的方式进行测试。具体来说，混合介子是由胶子量子数与夸克量子数相加而产生的，并且混合介子的子集预计具有简单夸克模型中不允许的奇异量子数组合。这是一项艰巨的任务，需要最近在加速器和探测器技术中成为可能的实验条件。 GlueX 通过采用独特的高强度偏振光子束和密封探测器来解决前者。后者受益于最近开发的完全不受磁场影响的大型硅基光电传感器。我们的团队在引导行业发展方面发挥了决定性作用，这些设备现已在亚原子、医疗和核安全领域投入商业应用。 GlueX计划是通过系统地研究传统介子和混合介子的所有衰变模式来绘制QCD谱。这项工作需要将最先进的实验结果与最先进的实验解释相协调。后者受到获得稳健理论描述的不确定性的限制，而不是我们对探测器或数据统计精度的理解。我们的小组将在现实世界数据稀疏或没有的地区进行低质量介子分析。这项研究将提供有争议的（过去统计功效较低的实验）以及未探索的介子光谱领域的数据。