Study of the B-Meson Lifetime and the Performance of the Outer Tracker at LHCb

The research in the dissertation addresses two issues: the overall performance of the LHCb Outer Tracker (OT) detectors as shown during quality checks and beam tests; the study of the lifetimes of B+ and B0 mesons at LHCb. Physics at the Large Hadron Collider (LHC) at CERN, Geneva requires high performance detectors. One of the four major LHC experiments is the Large Hadron Collider beauty experiment (LHCb). It is a dedicated B-physics experiment for precision measurements of CP violation in the B-meson system and for studying rare B decays. In order to efficiently reconstruct the trajectories of charged particles, LHCb is equipped with Outer Tracker (OT), consisting of gaseous straw tube detectors. The OT system comprises three stations each consisting of multiple layers of wires in vertical and non-vertical orientation. Basic unit of the stations is the OT module - a self-contained gas-detector unit filled with a counting gas mixture. The outer tracker module production was carefully monitored by variety of tests, forming the quality assurance and commissioning of the detector. The overall performance of the outer tracker detector as shown during the quality and beam tests is one of the topics of the dissertation. The second part of the dissertation is a research on the B-meson lifetimes at LHCb. The lifetimes au_{B+} and au_{B0} of B+ and B0 mesons are extracted in a simulation study, using the B+ -> J/psi K+ and B0 -& gt; J/]psi K* decay modes. The LHCb sensitivity to the au_{B+}/ au_{B0} ratio is defined. This ratio can be used as a probe for validating the Heavy Quark Expansion model.