Amplitude analysis of the Ds + pi - pi + pi + decay

In this thesis, the amplitude analysis of the D+s → π−π+π+ decay was performed to determine the π−π+ S-wave amplitude and the resonant structure of the P- and D-waves. The analysis is based on proton-proton collision data recorded by the LHCb experiment in 2012 at a centre-of-mass energy of 8TeV and corresponding to an integrated luminosity of 1.5 fb−1. The analysis includes the first observation of the following decay channels in the D+s → π−π+π+ decay: D+s → ω(782)π+, D+s → ρ(1700)0π+ and D+s → f′ 2 (1525)π+. The resonant structures of the D+s → π−π+π+ and D+→ π−π+π+ decays are also compared, providing information about the mechanisms for the hadron formation in these decays. Furthermore, technical contributions made to the LHCb experiment during the PhD studies, specifically in the preparation for the LHC Run 3, are described.