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

本项目主要通过电子散射实验研究核子的夸克-胶子结构。它将利用美国弗吉尼亚州杰斐逊实验室加速器的电子束，在实验室实验大厅B的一个固定目标上散射核子的高能电子（11 GeV）。该实验将作为CLAS合作实验计划的一部分进行，利用CLAS12探测器套件。在如此高的光束能量下，核子内部的夸克发生散射，产生一系列处于最终状态的粒子。这些都被检测到，然后用计算机程序分析数据，以确定感兴趣的反应通道。在这个博士项目的情况下，这将是从核子内部产生一个高能光子，作为散射（深度虚拟康普顿散射）的结果，或者在类似的过程中产生一个介子（硬独占介子产生）。对反应中不同横截面或不对称性的测量（通过使用电子束或两个相反极化的目标）可以得到有关核子基本结构的信息，以及其中夸克和胶子的分布，这反过来又赋予核子整体特性，如自旋和质量。这些性质是如何从基本的夸克-胶子分布中获得的，这是一个非常令人感兴趣的领域，其中许多仍是未知的。博士项目将包括在实验室采集数据，如果旅行限制允许的话（否则数据将由现场的同事采集），然后是实验的探测器校准，一段时间的数据分析伴随着散射过程的模拟，最后将对结果进行解释和发表。

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.