Measurements of spin asymmetries for deeply virtual compton scattering off the proton using the extended maximum likelihood method

Smith, Gary Douglas (2013) Measurements of spin asymmetries for deeply virtual compton scattering off the proton using the extended maximum likelihood method. PhD thesis, University of Glasgow.

Abstract

Generalised Parton Distributions (GPDs) provide a theoretical framework that promises to deliver new information about proton structure. In the impact parameter interpretation, they describe the substructure of the proton in terms of its quark (and gluon) constituents in three dimensions: two transverse spacial dimensions and one longitudinal momentum dimension. Through Ji’s sum rule, they offer a means by which to determine the total angular momentum contribution of quarks to the proton’s spin of h ̄ /2. GPDs are directly related to Compton Form Factors (CFFs), which are distributions that are measurable us- ing Deep Exclusive Scattering (DES) processes such as deeply virtual Compton scattering (DVCS). DVCS is characterised by the scattering of a single photon with large virtual- ity off a single quark (or gluon) inside the proton, resulting in the production of a hard photon: γ ∗ p → γ p′ . In this work, data recorded with the CLAS detector at Jefferson Laboratory during the EG1DVCS experimental run were analysed. This experiment ran for over 80 days with a longitudinally polarised electron beam and a solid NH3 target containing longitudinally polarised protons. The resulting data set accommodated pre- cise measurements of DVCS beam, target and double spin asymmetries, each of which is sensitive to different combinations of CFFs. The final results presented here are fits to these three asymmetries, which were performed using the Extended Maximum Like- lihood method. It is intended that these results will be used in the future, along with other DES asymmetry and cross-section measurements, to constrain CFFs and thus move towards a more complete understanding of the structure of the proton.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Proton Structure, Proton Substructure, Hadron Physics, Electron Scattering, Deeply Virtual Compton Scattering, Thomas Jefferson Accelerator Facility, Generalised Parton Distributions, Extended Maximum Likelihood, Spin Asymmetries, CEBAF Large Acceptance Spectrometer
• Subjects: Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Supervisor's Name: Ireland, Professor David and Murray, Dr. Morgan
• Date of Award: 2013
• Depositing User: Mr Gary Smith
• Unique ID: glathesis:2013-5042
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 24 Mar 2014 14:45
• Last Modified: 24 Mar 2014 15:02
• URI: https://theses.gla.ac.uk/id/eprint/5042