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

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.