J/Psi Photoproduction off the proton and neutron with CLAS12

使用 CLAS12 进行质子和中子的 J/Psi 光生产

• 批准号: 2284628
• 金额: --
• 依托单位: University of Glasgow
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2284628
• 关键词: Psi; Photoproduction; off; proton; neutron

Understanding hadronic structure and interactions in terms of quark and gluon degrees of freedom,within the framework of Quantum Chromodynamics (QCD), is the main goal of modernnuclear/hadron physics. An important tool to further explore these fundamental properties is thestudy of heavy quarkonia with hadronic matter. The production of heavy quarkonia directly probesthe local colour (gluonic) fields in the nucleon and can reveal properties such as their spatialdistribution (building a picture of the internal components of the nucleon), the response tomomentum transfer within the system (how does the picture vary with energy) and the correlationwith valence quarks (the quarks that give the nucleon its properties such as charge).The first state of heavy quarkonia is the two quark system comprising of a bound charm-anti-charmpair, namely the J/Psi meson. With the available beam energy at Jefferson Lab now upgraded to 12GeV and a new detector system, CLAS12 in Hall-B on-line, the photo- and electroproductionofJ/Psi can now be studied. There is a considerable amount of J/Psi photoproduction data at highenergies but no data near threshold. Given the considerable change in dynamics between highenergy and the near-threshold regions, two recent experiments carried out on a proton and adeuterium target at CLAS12 will provide unique information on the gluonic fields within thenucleon at "real-world" hadronic energy scales.In addition to the studies of these fundamental QCD degrees of freedom, recent claims of thediscovery of pentaquark (5 quark) like structures from the LHCb have renewed interest in thischarmonium threshold region. These states, should they exist, are within the energy range availablein the above measurements and this data has the potential to provide compelling evidence for oragainst such states. Furthermore, CLAS12 is in the unique position to provide measurements fromproduction off a neutron (within deuterium) and thus check the necessity for isospin invariance tohold true regarding any "new" resonance claims. In simple terms, if a pentaquark resonance isproduced decaying to a J/Psi and proton, then one must also exist which decays to J/Psi and aneutron.The project aims and objectives are currently defined to:Study the particle identification efficiency of the CLAS12 detector system through the analysis ofelectron-positron pairs.Develop a standard cuts based analysis for the dataDevelop a machine learning algorithm to replicate and verify the above standard approach. Theexploitation of machine learning is still in its infancy within the hadronic physics community andany such development will provide valuable guidance for future analysis projects.Ultimately extract the cross-sections (the production probabilities) of J/Psi-proton and J/Psineutron.The project will be undertaken within the CLAS Collaboration at Jefferson Lab.

在量子色动力学（QCD）的框架内理解强子结构和夸克和胶子自由度的相互作用是现代核/强子物理学的主要目标。进一步探索这些基本特性的一个重要工具是用强子物质研究重夸克尼亚。重夸克尼亚的产生直接探测核子中的局域色（胶子）场，并可以揭示诸如它们的空间分布（构建核子内部组件的图像）、系统内动量传递的响应（图像如何随能量变化）以及与价夸克（赋予核子其性质如电荷的夸克）的相关性等特性。重的第一态 夸克尼亚是由一对束缚的魅力-反魅力对组成的双夸克系统，即 J/Psi 介子。随着杰斐逊实验室的可用光束能量现已升级到 12GeV 以及 Hall-B 中的新探测器系统 CLAS12 在线，现在可以研究 J/Psi 的光和电产生。有大量高能 J/Psi 光生产数据，但没有接近阈值的数据。考虑到高能和近阈值区域之间动力学的巨大变化，最近在 CLAS12 的质子和氘靶上进行的两项实验将提供有关“真实世界”强子能量尺度的核子内胶子场的独特信息。除了对这些基本 QCD 自由度的研究之外，最近关于发现五夸克（5 夸克）的主张 大型强子对撞机的结构重新引起了人们对这个鲲阈值区域的兴趣。这些状态（如果存在）位于上述测量中可用的能量范围内，并且该数据有可能为支持或反对这些状态提供令人信服的证据。此外，CLAS12 处于独特的位置，可以提供中子（氘内）产生的测量，从而检查同位旋不变性对于任何“新”共振主张是否正确的必要性。简单来说，如果产生了五夸克共振，衰变为 J/Psi 和质子，那么也必然存在衰变为 J/Psi 和中子的五夸克共振。该项目的目的和目标目前定义为：通过分析电子-正电子对，研究 CLAS12 探测器系统的粒子识别效率。开发基于标准切割的数据分析。开发机器学习算法 复制并验证上述标准方法。机器学习的开发在强子物理界仍处于起步阶段，任何此类发展都将为未来的分析项目提供有价值的指导。最终提取 J/Psi 质子和 J/Psineutron 的横截面（产生概率）。该项目将在杰斐逊实验室的 CLAS 合作组织内进行。