Hadron Spectroscopy in the Light Quark Sector at GlueX

亚原子物理学寻求在最基本的层面上理解自然及其所有规律，直到它的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，这让我们更加坚信，被称为标准模型的基本模型基本上是对亚原子世界的有效描述，但不一定是一个完整的描述。在标准模型的四种力中，原子核内的强力被称为量子色动力学(QCD)的理论所理解。QCD描述了夸克和胶子相互作用的物理基础，它似乎允许丰富的允许成分的光谱，而自然更倾向于揭示更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。到目前为止，只观察到了无色的“夸克模型”状态--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到或被抑制。但QCD预测了更多类型的状态，而不仅仅是介子和重子。GlueX实验的目标是产生和识别未知的奇异物质形式，这些物质在所有其他粒子中显示出独特的特征，这将使QCD能够以约束的方式进行测试。具体地说，混合介子是由胶子量子数与夸克量子数相加而产生的，据预测，混合介子的子集具有简单夸克模型中不允许的奇异量子数组合。这是一项困难的任务，需要最近在加速器和探测器技术中实现的实验条件。GlueX正在通过使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。我们的团队在指导工业发展方面发挥了决定性作用，这些设备现在可以在亚原子、医疗和核安全领域进行商业使用。GlueX计划是通过系统地研究常规介子和混合介子的所有衰变模式来绘制QCD谱。这一努力需要使最先进的实验结果与最先进的实验解释相协调。后者受到获得可靠的理论描述的不确定性的限制，而不是我们对探测器或数据的统计精度的理解。我们的团队将继续对低质量介子进行分析，在那些缺乏或没有真实数据的地区。这项研究将提供有争议的(过去低统计能力的实验)以及介子光谱学中未探索的领域的数据。

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.