DVCS at HERMES: The recoil detector & transverse target spin asymmetries

University of Glasgow, Diss., 2007; 129 pp., (2007). doi:10.3204/DESY-THESIS-2008-006
The HERMES experiment is a large forward angle spectrometer located at the HERA accelerator ring at DESY, Hamburg. One of the most exciting topics studied at HERMES is Deeply Virtual Compton Scattering (DVCS) which is the simplest interaction that provides a gateway for access to Generalised Parton Distributions (GPDs). GPDs are a theoretical framework which can be used to calculate the total angular momentum of the quarks in the nucleon. As such, they provide one piece of the puzzle of nucleonic spin structure. In 2005, HERMES was upgraded in the target region with a Recoil Detector that allows it to make truly exclusive measurements of the DVCS interaction for the rst time. The design and construction of the Recoil Detector is discussed herein, in addition to a complete analysis of the Transverse Target Spin Asymmetry (TTSA) in DVCS. Experimental facilities that enable measurement of this asymmetry are rare. The importance of the information on the TTSA from HERMES is made yet greater as the transversely polarised target that allows the asymmetry to be measured has been replaced by an unpolarised target. This was to allow the Recoil Detector to be installed. The nal stage of this thesis shows a model-dependent method for constraining the angular momentum of the quarks in the nucleon and speculates as to the other pieces of the spin puzzle.
Published by Deutsches Elektronen-Synchrotron, DESY, Hamburg