Spatial and vertex resolution studies on the ATLAS Pixel Detector based on Combined Testbeam 2004 data

This diploma thesis deals with spatial and vertex resolution studies on the ATLAS Pixel detector based on real data taken during the Combined Testbeam period 2004 (17th May - 15th November). For the Combined Testbeam a barrel segment of the ATLAS Detector was build up and tested under real experimental conditions. Several data sets, being recorded during that time, are reconstructed by the ATLAS control framework called ATHENA. The input information for the reconstruction of the particle tracks through the Pixel Detector are the so-called spacepoints. Their uncertainty affects the resolution of the reconstructed particle tracks and thus, also the accuracy of the vertex reconstruction. Since traversing particles deposite their charge mostly (but not compellingly) within more than one pixel, all pixels corresponding to one hit have to be grouped together to a cluster. To compute the spacepoint from the cluster information two different strategies can be performed. The first one is a digital clustering, with the resulting spacepoint being the geometrical center of mass of the cluster. The uncertainty of this spacepoint, which is also the spatial resolution, is defined by the pixel pitch devided by √12, that is ∼ 14 µm . Within the bounds of this work the spatial resolution of the spacepoint will be improved by a refined clustering. This second strategy takes into account the measured charge deposition within each pixel. The implementation of this improved track reconstruction and the results concerning the spatial and vertex resolutions are presented in this diploma thesis.