Searches for top-antitop quark resonances in semileptonic final states with the cms detector

Resumen

This thesis presents the results of two searches for a top-antitop quark (ttbar) resonance in semileptonic final states using data collected by the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC). Evidence of resonant ttbar production would represent a clear sign of new physics beyond the Standard Model of particle physics. The first search is based on the full data set recorded by the CMS experiment in proton-proton (pp) collisions at a center-of-mass energy of sqrt(s)=8 TeV during the LHC Run-1, for a total integrated luminosity of 19.7 fb-1. The second search considers 2.6 fb-1 of pp collisions data recorded by the CMS experiment in the first year of the LHC Run-2 (2015) at the higher center-of-mass energy of sqrt(s)=13 TeV. Both analyses make use of state-of-the-art techniques for the identification of top quarks produced with large transverse momentum. This approach maximizes the sensitivity of the analyses for high-mass X->ttbar resonances (M_X > 1 TeV), which are characterized by the production of an increasing fraction of top quarks in the boosted regime. The thesis also presents a set of studies on the use of the angular observables of the ttbar system and the treatment of interference effects in X->ttbar searches. No evidence for resonant ttbar production is found in the data sets considered and the invariant mass spectrum of the reconstructed ttbar system is used to set upper limits on the production cross section of a X->ttbar resonance in various new physics models.