Studies for a time projection chamber for the international linear collider and measurement of beauty cross sections in deep inelastic scattering at HERA

In the first part of this thesis a study of the possibility to use Gas Electron Multipliers (GEMs) for the readout of a TPC at high magnetic fields in presented. For this study a TPC prototype was designed and built, which allows for measurements in a 5 T magnet. First the functionality of this prototype will be demonstrated by means of a collection of performance measurements. Finally, first results of the point resolution measurements in the presence of high magnetic fields are presented. In the second part of this thesis the results of the measurements of the total and differential beauty cross sections in deep inelastic scattering (2 < Q2 < 100 GeV2) will be presented. The data used was collected in the years 1999/2000 with the H1 detector at the ep collider HERA and corresponds to an integrated luminosity of 43 pb-1. The semi-muonic decay channel of the b-flavoured hadrons is chosen for the analysis: ep → ebbX → eμj(j)X'. Events are selected containing the scattered positron, a muon identified in the central muon system and either one jet in the Breit frame or two jets in the laboratory frame. The fraction of the beauty signal in the data sample selected is determined from the distributions of the muon's signed impact parameter and the relative transverse momentum between the muon and the associated jet. The cross sections derived from this are compared with Next-to-Leading order QCD predictions. The measured cross sections are found to be above the NLO QCD calculations. (orig.)