Development and Commissioning of the Silicon Pixel GigaTracker for the NA62 Experiment at CERN

This dissertation focuses on the development and commissioning of the Giga- Tracker. The project is part of a larger research programme dedicated to the measurement of the rare $K^{+} \to \pi^{+} \nu \bar\nu$ decay branching ratio. The text is organized as follow: in Chapter 1 we review the unique characteristics of the rare $K^{+} \to \pi^{+} \nu \bar\nu$ decay as well as the NA62 experimental setup. Silicon pixel detectors are discussed in Chapter 2; we collect the important formulae we need for the discussion. A special emphasis is put on radiation damage and on the time resolution of silicon sensors. The aspects of this work related to the GigaTracker development are grouped in Chapter 3. Finally, the Chapter 4 is mostly dedicated to the study of the GigaTracker performances. We close the text with a firrst exploration of the NA62 2014 pilot run data.