Lepton Flavour Violation searches and scintillating fibre tracker testing in LHCb

This thesis presents new results on searches for lepton-flavour-violating particle decays, performed in the LHCb experiment at CERN. Two analyses are discussed in detail. The first one concerns the B 0 → e ± μ∓ decay. No evidence (s) of signal is observed and two upper limits are set, respectively for the B0 and Bs0 mesons: B(B0 → e±μ∓) < 1.0(1.3) × 10−9 and B(Bs0 → e±μ∓) < 6.0(7.2) × 10−9. The second analysis concerns the baryon sector: the Λ0b → Λ0e±μ∓ decay is searched. This study is currently under review in the LHCb collaboration. The whole procedure is described here in detail. Furthermore, the present thesis contains a description and the results of the quality assurance process for the production of mats of scintillating fibres for the SciFi, a new tracker for the LHCb detector developed in view of the Run III of LHC.