Exclusive $\rho^0$ meson cross section ratios on deuterium and hydrogen targets

The HERMES experiment is a large forward angle spectrometer located at the HERA accelerator ring at DESY, Hamburg. This thesis presents the analysis of the kinematic dependencies of 0 vector meson production on hydrogen and deuterium targets. The relative gluon and quark contribution to the 0 production amplitude is expected to depend on the kinematical variable xBj , and by measuring the ratio of 0 electroproduction cross sections on deuterium and hydrogen from HERMES data this dependence is conrmed. This thesis describes the methods used to extract the cross section ratio from the HERMES data taken between the years 1996 and 2000 and compares the results with the theoretical predictions. Until 2005 the missing mass resolution of the HERMES spectrometer was only suf- cient to allow exclusivity at the level of a data sample. The HERMES Recoil Detector, installed in early 2006, is an upgrade which will augment the HERMES spectrometer by establishing exclusivity at the event level and therefore improving the resolution to which various kinematical variables may be reconstructed. Additionally, the Recoil Detector will contribute to the overall background suppression capability of the HERMES spectrometer. These improvements will provide a strong reduction in the statistical uncertainties present in the 0-analysis and other analyses at HERMES. The Recoil Detector critically relies on its track reconstruction software to enable its capability to provide event level exclusive measurements. This tracking code is presented in detail