Studies of hadronic structure using electromagnetic probes

使用电磁探针研究强子结构

• 批准号: SAPIN-2021-00026
• 负责人: Huber, Garth
• 金额: $ 8.01万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 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=762493
• 关键词: Studies; hadronic; structure; using; electromagnetic

One of the central problems of modern physics research concerns our understanding of the building blocks of the atomic nucleus - the protons, neutrons, and other particles (mesons) that bind them. Notable discoveries have indicated that these particles consist of yet more fundamental constituents, the quarks and gluons. While a very good theoretical framework (called Quantum Chromo-Dynamics, or QCD) is able to accurately describe how quarks and gluons interact at extremely high energies (or, equivalently, when the quarks are very close together), it has been very difficult to apply QCD to lower energy (longer distance) phenomena. One of the obstacles to our improved comprehension has been a lack of quality data, particularly for the Deep Exclusive Reactions, which provide the clearest picture of the inner workings of QCD. Jefferson Lab enables these studies with its continuous, high luminosity electron beams, and detectors with good particle identification and reproducible systematics. 1. p+ and K+ Elastic Form Factors (Fp, FK): The internal structures of the two lightest mesons are parametrized by their form factors, and are critical hadronic structure quantities to understand. The p+ form factor offers our best hope of directly observing QCD's transition from strong-confinement at long-distance scales to asymptotic-freedom at short-distances. The K+, where the d quark is replaced with an s quark, provides a vital second study case.  Objectives: (i) establish the reliability of the extraction of the meson form factors from electroproduction data over a broad kinematic range, (ii) obtain high quality form factor measurements to high momentum transfer. The K+ data were acquired in 2018-19, while the p+ data were partly acquired in 2019, with the bulk to be acquired in 2021, 2023. The data are being analyzed by four Regina PhD students. 2. Unique Access to u-Channel Physics: Backward-angle meson electroproduction is anticipated to offer unique access to the three quark plus sea component of the nucleon wave function. We pioneered a new technique, which demonstrated the feasibility of high quality measurements in this previously unexplored region. Our upcoming experiment will take ?, ? and f data with goals: (i) establish existence of a backward-angle cross section peak for multiple reaction channels; (ii) extract the separated cross sections over a wide kinematic range; and (iii) establish whether the collinear factorization scheme is valid. 3. Study of Generalized Parton Distributions (GPDs):  SoLID (Solenoidal Large Intensity Device) will allow new data to be acquired on GPDs, "universal objects" providing a comprehensive description of the quark and gluon structure of the nucleon. Regina students will participate in SoLID detector construction and testing, planned for 2022-25, and contribute to our experiment probing the poorest known GPD, E-tilde. Funds are requested for Jefferson Lab fieldwork, PhD student and PDF salary support.

现代物理研究的主要问题之一是我们对原子核的构建基础的理解 - 质子，中子和其他粘合它们的颗粒（介子）。著名的发现表明，这些颗粒由更基本的宪法，夸克和麸质组成。尽管一个非常好的理论框架（称为量子铬动力学或QCD）能够准确地描述夸克和麸质如何在极高的能量（或同样，当夸克非常接近时）相互作用，但很难将QCD应用于降低能量（长度距离）现象非常困难。我们改善理解的障碍之一是缺乏质量数据，特别是对于深层的独家反应，这为QCD的内部工作提供了最清晰的景象。杰斐逊实验室（Jefferson Lab）凭借其连续的高光度电子束以及具有良好粒子识别和可再现系统的检测器来实现这些研究。 1。P+和K+弹性形式因子（FP，FK）：两个最轻的介子的内部结构以其形式因素参数化，并且是要理解的关键HADRONIC结构数量。 P+外形效果是我们最大的希望，即直接观察QCD从长距离尺度上的强量转变为短距离的非对称自由。 d夸克用S夸克取代的K+提供了重要的第二个研究案例。目的：（i）在广泛的运动范围内从电源数据数据中提取介孔形式的可靠性，（ii）获得高质量的外形尺寸测量到高动量传递。 K+数据是在2018 - 19年获得的，而P+数据是在2019年获得的，其中大量将于2021年，2023年获得。 2。独特的访问U通道物理学：向后角度的介子电源预计将为核波功能的三个夸克和海洋组件提供独特的访问。我们开创了一项新技术，该技术证明了在以前出乎意料的区域中高质量测量的可行性。我们即将进行的实验会接受吗？，？和具有目标的F数据：（i）建立多个反应通道的向后角截面峰； （ii）在宽的运动学范围内提取分离的横截面； （iii）确定共线分解方案是否有效。 3。对广义Parton分布（GPD）的研究：实心（螺线管大强度设备）将允许在GPD上获取新数据，该数据提供了对核的夸克和麸质结构的全面描述。里贾纳（Regina）的学生将参加固体探测器的建设和测试，计划于2022-25进行，并为我们的实验做出贡献，探讨了最糟糕的GPD E-Tilde。要求为Jefferson Lab Fieldwork，PhD学生和PDF薪水支持提供资金。