The study of nucleon structure through electron scattering at Jefferson Lab.

该项目的重点是通过电子散射实验研究核子的夸克-胶子结构。它将使用美国弗吉尼亚州杰斐逊实验室加速器的电子束，在实验室的实验大厅B的固定靶中散射来自核子的高能电子（11 GeV）。该实验将作为CLAS合作实验方案的一部分，利用CLAS 12探测器套件进行。在如此高的光束能量下，核子内部的夸克发生散射，产生一系列处于终态的粒子。这些被检测到，然后使用计算机程序分析数据以识别感兴趣的反应通道。在这个博士项目的情况下，这将是从核子内产生高能光子，作为散射的结果（深度虚拟康普顿散射）或在类似过程中产生介子（硬排斥介子生产）。通过测量反应中的微分截面或不对称性（通过使用电子束或两个相反极化的靶），可以获得有关核子的基本结构、夸克和胶子在其中的分布的信息，这反过来又给出了核子的整体性质，如自旋和质量。如何从夸克-胶子分布中获得这些性质是一个非常有趣的领域，在那里还有很多未知数。如果旅行限制允许，博士项目将包括在实验室获取数据（否则数据将由同事现场采集），然后是实验的检测器校准，延长的数据分析时间，并模拟散射过程，并将最终解释结果和出版物。

The project is focussed on studying the quark-gluon structure of the nucleon, through electron scattering experiments. It will use the electron beam at the Jefferson Lab accelerator in Virginia, USA, to scatter high energy electrons (11 GeV) from nucleons in a stationary target in the experimental Hall B of the laboratory. The experiment will be carried out as part of the CLAS Collaboration experimental programme, making use of the CLAS12 suite of detectors. At such high beam energies, scattering takes place from the quarks inside the nucleon, producing a range of particles in the final state. These are detected and the data is then analysed using computer programs to identify a reaction channel of interest. In the case of this PhD project, this will be either the production of a high energy photon from within the nucleon, as a result of the scattering (Deeply Virtual Compton Scattering) or the production of a meson in a similar process (Hard Exclusive Meson Production). Measurements of differential cross-sections or asymmetries (from using electron beams or targets of two opposite polarisations) in the reaction yield information about the underlying structure of the nucleon, the distributions of the quarks and gluons within it, which in turn gives the nucleon its global properties, such as its spin and mass. Just how those properties are obtained from the underlying quark-gluon distributions is an area of extreme interest, where much is still unknown.The PhD project will consist of data-taking at the laboratory, if the travel restrictions allow it (otherwise data will be taken by colleagues on-site), followed by detector calibrations for the experiment, an extended period of data analysis accompanied by simulations of the scattering process, and will culminate in the interpretation of the results and publication.