Development of ring imaging Cherenkov detectors for the LHCb experiment

This thesis reports on work done as part of the development of the Ring Imaging Cherenkov (RICH) detectors of the LHCb experiment. The context of this work is set out in Chapter 1, which includes an overview of the physics of CP violation, followed by a discussion of other experiments that study B physics. LHCb itself is then described, with particular emphasis on its RICH detectors, and the photon detectors to be used therein. The work done by the author to ensure an adequate shielding of the photon detectors in the two RICH detectors from the magnetic fields produced by the LHCb dipole is then presented. A candidate photodetector for the RICH is the Pixel HPD. The author's contribution to the upgrade of the HPD test system to operate at the LHC bunch-crossing rate of 40MHz is the subject of the following section. This system was used to investigate and optimise a method of minimising the threshold distribution of the Pixel HPD's encapsulated readout chip. The final chapter of the thesis concerns the aerogel radiator of the upstream RICH detector. The results of a test-beam experiment to measure the properties of some candidate aerogel samples are presented, along with simulation studies motivated by the test-beam results. The effect of an unexplained increase in the Cherenkov angle error observed at the test-beam on the channel Bs->DsK is simulated, followed by an investigation into the consequences for that channel of altering the aerogel length and clarity. A study into the effects on the RICH reconstruction performance due to the effects of delta-ray generation within the aerogel are presented. The thesis concludes with a summary and suggestions where further investigation is necessary.