Étude de la violation CP dans des processus au LHC 
qui brisent la conservation du nombre leptonique
This thesis is dedicated to the study of CP violation in these processes ūd→tb̄ e⁻ μ⁻ et W⁻→ l-1 l-2 (q′¯ q)⁺.   There are experiments which search to identify these processes at the "Large Hadron Collider" (LHC). The outcome of the observation of these decays would imply violation of lepton number conservation, ∆L = 2. If the neutrino is a Majorana particle, it is its own antiparticle and we can observe processes that violate the conservation of the lepton number, ∆L = 2. The neutrinoless double beta decay (0νββ), is a process which is characterized by ∆L = 2, occurs when the neutrinos are Majorana particles. If we observe 0νββ-like processes at the LHC, there is also the possibility of looking for CP violation. Measuring this type of CP violation would give us information about New Physics that could not be easily obtained using other methods. There are three types of CP violation, namely: direct, indirect and kinematic (triple product). This research presents studies concerning direct and triple product CP violation. The first paper is devoted to triple products in the process: ūd→tb̄ e⁻ μ⁻. In addition, the model considered does not involve a Majorana neutrino. Using MadGraph, we have numerically studied and evaluated the CP violation for the two mentioned processes for three types of accelerators: high luminosity HL-LHC (14 TeV), high energy HE-LHC (27 TeV) and for a future FCC-hh collider (100 TeV). We found that the triple product is not measurable at the HL-LHC, may be measurable at HE-LHC, and is certainly measurable at FCC-hh. In the second article, we investigated to see how to generate CP violation with right-handed neutrinos. The second article is on the study of direct CP violation the decay W⁻→ l-1 l-2 (q′¯ q)⁺   by involving two neutrinos N1and N2. It is also observed that the value of CP asymmetry can be measured with an accuracy of 3σ and as 0.1% ≤ ACP ≤ 10%.
Leptoquark Majorana Neutrino CP Violation Leptoquark Triple Product