Measurement of the angular distribution of the B+ → π+μ−μ+ decay and R&D towards a future upgrade of the particle identification system of the LHCb experiment

This thesis presents two complementary research studies, linked by the LHCb experiment. A first analysis of the angular distribution of the B+ → π+μ+μ− decay with LHCb Run 1 and 2 data is presented, using the Feldman-Cousins approach to ensure correct coverage of the angular observables measured, AFB and FH. This decay is a rare b→ d quark flavour changing neutral current process. The analysis is at an advanced stage and blind at the time of writing of this work. The analysis strategy is tested on control modes and pseudo-experiments. Sources of systematic uncertainties are identified and their effects evaluated. In addition, studies for the R&D effort for the development of a new time-of-flight Cherenkov detector, TORCH, proposed for the next LHCb upgrade are presented. The proposed design uses MCP-PMTs to measure single photon time. The TORCH MCP-PMT is characterised with studies of uniformity and gain. The single photon time resolution of the TORCH MCP-PMT coupled to readout electronics has been measured, resulting in (47.5 ± 0.7) ps, meeting the TORCH design requirement.