Measurement of deep exclusive meson-production in electron scattering off a neutron using CLAS12 at Jefferson Lab

Lead Research Organisation: University of Glasgow
Department Name: School of Physics and Astronomy


The project is the study of nucleon structure through the experimental measurement of meson electro-production from the neutron. The experiment, run by the CLAS collaboration, will take place in Hall B of Jefferson Lab, USA, in 2019. It will use the lab's 10.6 GeV polarised electron beam, the CLAS12 detectors and a fixed deuterium target.

Deep exclusive meson-production is a process in which a high energy electron scatters from the partons (at the energies available in this experiment they are valence quarks) inside the nucleon, and a high-momentum meson is produced as a result. Analysis of the cross-sections and asymmetries due to different polarisation states of the beam or target carry information about spatial and momentum distributions of the partons in the nucleon. Specifically, deeply virtual meson production yields information on Generalised Parton Distributions (GPDs), which correlate longitudinal parton momentum to their transverse position. As such, determination of GPDs enables 3D, tomographic imaging of the nucleon. GPDs also carry information on the composition of nucleon spin (unknown, beyond the fraction contributed by the intrinsic spin of quarks). The GPDs have recently also been linked to pressure distributions within the nucleon, opening an entirely new way of studying nucleon structure.

The project will most likely focus on the analysis of beam-spin asymmetry in the deeply virtual production of neutral pions from the neutron. The production of a negative pion from the neutron is also under consideration (with the recoiling nucleon being a proton in this case). The student project will involve data-taking at Jefferson Lab, calibration of the Central Neutron Detector and analysis of the data for the extraction of the observable(s). The aim is a publication towards the end of the thesis project.

Type of activity
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- Exploitation and experiment %100
- Investment in new instrumentation, facilities or techniques
- Operation & maintenance of facilities
- Theory

Student classification
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- Astronomy
- Nuclear Physics. X
- Particle Astrophysics


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
ST/S505390/1 01/10/2018 30/09/2022
2126391 Studentship ST/S505390/1 01/10/2018 31/03/2022 Paul Naidoo