RICH detector time alignment and studies of CP violation in the decay B0s → ØØ at the LHCb experiment

LHCb is a high-precision experiment dedicated to measuring the decays of B hadrons. Particle identification at LHCb relies upon two Ring Imaging Cherenkov (RICH) detectors, and this thesis describes work carried out relating to these detectors. It includes an analysis performed to investigate ion feedback in the Hybrid Photon Detectors (HPDs) used as photosensors for the RICH system, and studies of the performance of a RICH prototype in test beam conditions. A time alignment system for the RICH detectors has been designed and implemented, and this work is presented here. Excellent particle identification performance is required for efficient reconstruction of the b → s penguin decay B0s → ØØ a channel in which visible New Physics effects are possible. An analysis of this decay has been performed, encompassing event selection at trigger and offline levels, resolution, tagging and acceptance studies, and toy monte carlo experiments on sensitivity and systematic errors in measuring the total weak phase. The results are discussed within