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Deeply virtual compton scattering off longitudinally polarised protons at HERMES

Mahon, David Francis (2010) Deeply virtual compton scattering off longitudinally polarised protons at HERMES. PhD thesis, University of Glasgow.

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Abstract

This thesis details the simultaneous extraction of three polarisation-dependent asymmetries in the distribution of real photons from the e p → e p γ interaction and its indistisguishable deeply virtual Compton scattering and Bethe-Heitler processes at the HERMES fixed-target experiment at Desy. The data analysed were taken using a longitudinally polarised 27.57 GeV positron beam incident on a longitudinally polarised hydrogen gas target. The extracted asymmetries include two single-spin asymmetries A_UL and A_LU which depend on the polarisation of the target and beam respectively, averaged over all other polarisation states. The double-spin asymmetry A_LL dependent on the product of the beam and target polarisations is extracted for the first time. The asymmetry amplitudes extracted relate to combinations of Generalised Parton Distributions (GPDs), predominantly H and Htilde. The extracted amplitudes will be presented across the HERMES kinematic range alongside theoretical predictions from a GPD model based on double distributions. Large sin phi and cos(0phi) amplitudes are observed for A_UL and A_LL respectively, with an unexpectedly large sin(2phi) amplitude for A_UL . The results for the A_UL and A_LL asymmetries are broadly compatible with theory predictions, and the extracted A_LU amplitudes are compatible with HERMES results extracted from a significantly larger data set. It is foreseen that these results will form input to future global data-based GPD models which aim to provide a better understanding of GPDs.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Deeply virtual Compton scattering, Generalised parton distributions, nucleon structure, lepton nucleon scattering
Subjects: Q Science > QC Physics
Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
Supervisor's Name: Kaiser, Prof. Ralf
Date of Award: 2010
Depositing User: Mr David F Mahon
Unique ID: glathesis:2010-1924
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 22 Jun 2010
Last Modified: 10 Dec 2012 13:48
URI: http://theses.gla.ac.uk/id/eprint/1924

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