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Title: Deeply virtual compton scattering off longitudinally polarised protons at HERMES
Author: Mahon, David Francis
ISNI:       0000 0004 2684 034X
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 2010
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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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics