Search for high-mass resonances decaying to heavy flavour jets

The main purpose of this thesis is to search for high-mass resonances decaying to a pair of heavy (b or c) jets. Data taken by LHCb experiment during Run II campaign in 2016 are analysed. The main challenge of this analysis is the determination of the Quantum Chromodynamics (QCD) multi-jet background: since the Monte Carlo (MC) simulation is not able to reproduce the heavy flavour di-jets characteristics, a data-driven technique is used, based on the identification of signal and control regions. The extrapolation of the background of the di-jets invariant mass shape from the control region to the signal region is performed with a transfer function, determined from MC samples. The QCD background model is validated with a fit to the signal region where the number of Z boson events is extracted. Results are compatible with the SM expectations. High-mass resonances decaying to heavy flavour di-jets (b b-bar and c c-bar) in the mass range between 45 and 175 Gev are considered: for each search, the number of events found is compatible with zero, and upper limit on the production cross section times branching ratio is set at 95% confidence level with the CLs method. For Higgs searches results are compared with SM expectations: the production cross section times branching ratio for b (c) quarks final state is 29 (42) times the SM value. Finally relevant upgrades on the LHCb detector and new analysis techniques based on neural networks are presented.