Search for ttbar resonances at sqrt(s) = 8 TeV with the CMS experiment at LHC

This work concerns the search for the production of heavy resonances decaying into ttbar pairs at a the center-of-mass energy √s = 8 TeV in the CMS experiment at LHC. After the Higgs boson discovery, a persisting issue in the Standard Model is the squared divergencies of the Higgs mass, that generate the “hierarchy problem”. This divergence is mitigated by the Supersimmetry or, in other models, introducing the Kaluza-Klein gluonic resonances or Z massive resonances with higher coupling with the most massive particles. For this reason, the ttbar decay is the channel with the highest cross section. The models predict a mass of these resonances between 700 GeV and some TeV, and production cross sections around some picobarns. The CMS data collected at √s = 8 TeV center-of-mass energy with integrated luminosity L= 19.5 fb^(-1) represent a large sample of data on which it is possible to look for a possible tt resonances. In this thesis, the search is performed in the all-jets channel with reference to the resolved event topology characterised by 6 or more jets in the final state.