Flavour tagging with baryons and a study of two body $\Lambda_b$ decays with the LHCb experiment

The LHCb experiment will perform precision measurements of CP-violation and search for rare B decays at the Large Hadron Collider (LHC), which is due to begin operation in 2008. The LHCb Ring Imaging Cherenkov (RICH) system provides the particle identification crucial for these studies. The Multi-Anode photomultiplier tube (MaPMT)is a candidate photon detector for the LHCb RICH system. Performance studies of the MaPMT in a charged particle beam at CERN demonstrate that the pulse shape of the BeetleMA readout ASIC does not return to zero after 125ns, which will lead to ghost pixel hits and the possible drift of the pedestal outside the dynamic range of the amplifier. Measurement of key CP asymmetries at LHCb requires that the flavour of the B-meson at creation is known. Flavour tagging using protons is shown to have potentially useful tagging performance, but the implementation is found to be challenging. A correlation between b-quark and Lambda flavour is observed for a Lambda produced in the same fragmentation process as a strange B-meson, analogous to a same-side kaon tag. A small, but non-negligible, tagging performance is attained. CP-violation asymmetries are expected in the b-flavoured baryon decays Lambda_b -> p pi and Lambda_b -> p K. Studies of the reconstruction and selection of these decay channel with Monte Carlo simulated data suggest an annual event yield of ~2k Lambda_b -> p pi and ~3k Lambda_b -> p K events. T he R-parity violating Minimal Supersymmetric Standard Model is expected to suppress the CP asymmetry of Lambda_b -> p pi decays and enhance the branching fraction. Evidence for CP-violation consistent with the Standard Model is expected to require an integrated luminosity of more than 1.5 fb^{-1}, while evidence for CP-violation consistent with R-parity-violation in the Minimal Supersymmetric Standard Model will require 50 - 250 fb^{-1}; which in the latter case will only be achievable with an upgraded luminosity "Super"-LHCb detector.