CMS pixel module readout optimization and study of the Β⁰ lifetime in the semileptonic decay mode

After more than twenty years of development, the CERN Large Hadron Collider will start continuously operating in mid 2009. An enormous amount of high energy collisions will take place inside the CMS experiment. The innermost detector of this experiment is the barrel pixel detector, with its main goals of track and vertex reconstruction. To do this reconstruction with a high precision, the charge produced inside the silicon sensor is read out as an analog signal. In the first part of this work, the analog readout chain is optimized by setting digital-to-analog converters on the readout chip. Procedures are developed to apply this optimization on more than 10’000 readout chips for the entire detector. The optimization is verified by comparing all optimized chips and with a simulation studying the hit resolution inside the detector. In the second part of this work the lifetime measurement of the B0 meson is studied in the semileptonic decay mode using a new reconstruction method for the undetected neutrino appearing in this decay. Since the decay vertex of the B0 meson is a crucial input parameter for this method, an optimal analog readout is essential. Furthermore, the vertex resolution is optimized by comparing different fit methods. Various consequences of the neutrino reconstruction method are studied. Finally, the new method leads to a reconstruction of the B0 lifetime without introducing a bias.