[eng] The aim of the LHC and the Tevatron experiments is to search for new phenomena in elementary particles physics and, in particular, to reveal the mechanism responsible for the electroweak symmetry breaking. Despite being so far undiscovered, this mechanism might also be the source for the masses of the quarks and leptons. Due to its large mass, the top quark is thus a natural probe in this quest for new physics.
In this thesis, we have used effective field theories to explore the fundamental interactions between particles. After a first contact with a known effective theory in order to compute the η- η' mixing angle, this approach has been used for the search of new physics in top pair productions. The effective Lagrangians for both same and opposite top pair productions have been derived and their impact on the LHC and the Tevatron experiments explored.
The parameter space has been constrained from total ttbar cross-section measurements at both colliders and its invariant mass spectrum at the Tevatron. In particular, we have shown that the forward-backward asymmetry measured at the Tevatron can be explained in this frame independently of the other measurements. Moreover, same sign top pair production appears to be a promising channel for the discovery of new physics at the LHC. Finally, we have shown that the new interactions can also affect significantly the Higgs production.