Since the discovery of the Higgs boson in 2012, the predictions of the Standard Model regarding of new particles have been completed. The Standard Model is currently the most accurate theory for describing the fundamental particles and their interactions, but it is known that it does not explain multiple observed phenomena and there is no direct evidence of new particles nor interactions. Probably one these phenomena regards the Lepton Flavour Universality, that has been found to be broken at the evidence level in measurements involving decaying hadrons originated from bottom quarks, or in the muon magnetic moment. Motivated by the anomalies found in the bottom quark sector, this study explores the top quark sector in the context of an effective theory. Two-quark-two lepton effective interactions involving the top quark, that could be produced by leptoquarks or a Z boson, could explain the anomalies. The first search is made with the pp ! ttll process at the Large Hadron Colliders and the High-Luminosity Large Hadron Collider, introducing two-quark-two-lepton effective operators in the Standard Model Lagrangian. The key point of this analysis is the requirement that the invariant mass of the lepton pair must be greater than 100 GeV, thus reducing the production of a Z boson that decays leptonically and the effective production via two-fermion operators in a global analysis. The second search is contained in the Snowmass White Paper: prospects for the measurement of top-quark couplings report, as the Master’s Thesis contributed to it. In a similar way, multiple effective operators have been studied in the Large Hadron Collider and the High-Luminosity Large Hadron Collider, but mainly in proposed future electron-positron colliders.
