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Title: First measurement of the E double-polarisation observable for γn → K+Ʃ - with CLAS & a new forward tagging hodoscope for CLAS12
Author: Fleming, Jamie Alan
ISNI:       0000 0004 6421 0840
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2016
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Establishing the excitation spectrum of the nucleon would be a key advance to further our understanding of nucleon structure and Quantum Chromodynamics (QCD). Recent theoretical advances allow predictions of the excitation spectrum of the nucleon and other nucleon properties directly from QCD in the non-perturbative regime, via numerical methods (such as Lattice QCD), complementing existing constituent quark models. There is an ongoing world programme in meson photoproduction from the nucleon, which has already led to a number of nucleon resonances being discovered and established. This advance has largely been made possible by the first accurate measurement of polarisation observables. Available data has been obtained for proton targets, whereas for a complete picture of meson photoproduction, data from the neutron must also be obtained. This is important, as nucleon resonances can have very different photo-couplings to the proton and neutron. This thesis presents the first measurement of the E double-polarisation observable for the exclusive γn → K+Ʃ- reaction using a polarised hydrogen-deuterium target from the g14 run period at CLAS. Circularly polarised photons of energies between 1:1 and 2:3 GeV were used, with results shown in 200 MeV bins in Eγ and bins of 0:4 in cos θC.M./K+. Further to this, CLAS has undergone a detector upgrade in order to facilitate electrons of up to 12 GeV from Jefferson Lab's upgraded accelerator. Essential to this, is a new system for tagging quasi-real photons by detecting electrons scattered at very small angles. My work includes significant contributions to the design, realisation and construction of a hodoscope for this forward photon tagging apparatus. Presented in this thesis is a comprehensive overview of my work in developing and constructing the scintillating hodoscope for the CLAS12 Forward Tagger.
Supervisor: Watts, Daniel ; Murphy, Alex Sponsor: Science and Technology Facilities Council (STFC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: polarisation observables ; E ; CLAS ; Forward Tagger ; HDice ; CLAS12 ; hodoscope