Constraining the Higgs and heavy neutral lepton sectors with the CMS detector

This thesis deals with Beyond the Standard Model (BSM) scenarios with both displaced and prompt signature. For the displaced signature a Heavy Neutral Lepton analysis in the semileptonic final state is performed. I am looking for right-handed neutrinos with mass between 1 and 15 GeV. Those particles are accommodated in Majoran and Dirac hypothesis, exclusion limits on the mass and on the lepton-neutrino coupling are presented for both models. On the other hand, also BSM scenarios with prompt signature are investigated within the Higgs framework. A ttH multileptonic differential analysis is presented targeting both EFT results and SM unfolding results. Deep Neural Network is largely use for regression and to discriminate SM for EFT signature. Following the stream of investigating the Higgs properties a HH analysis in bb4l final state is presented. This analysis takes the advantage of a very clear signature and a small amount of background that maximise the sensitivity search, limits on the anomalous values of the Higgs trilinear coupling and on the SM hypothesis are shown. All these analyses target the full Run2 dataset of the CMS experiment