Search for new physics in events with high transverse momentum leptons with the CMS detector at the LHC

This thesis presents both measurements of SM processes and searches for BSM physics in events with high momentum leptons collected in the CMS detector of the LHC. These studies use proton-proton collision data at $\sqrt{s}$=13 TeV collected during the Run 2 of the LHC. Measurements of the production cross section of a top quark associated with a W boson have been performed. An inclusive cross section of $\sigma$ = 63.1 $\pm$ 1.8 (stat) $\pm$ 6.3 (syst) $\pm$ 2.1 (lumi) pb has been measured, consistent with the SM prediction. Differential measurements of this process have also been conducted, and found to be consistent, within uncertainties, with the SM. Searches for BSM physics have been performed in events with two opposite-sign same-flavor leptons and large momentum imbalance. The choice of this final state is motivated by several SUSY signatures, for which specific signal regions are built. No significant excess of data above the SM prediction is observed in the signal regions. Therefore, upper limits to sparticle production in the context of simplified SUSY models are set. Finally, a measurement of the production of single and pairs of top quarks in association with a Higgs boson is presented in the multilepton channel. This channel targets the decay of the Higgs boson into WW, ZZ and ττ pairs. Regions enriched in signal and in the various backgrounds are constructed by classifying events exploiting kinematic differences between the two species. Results allow to observe ttH production with an observed (expected) significance of 4.7 (5.2) standard deviations. The measurement is also interpreted in the context of Higgs coupling modifiers, constraining κ_t to be in either one of the intervals $-0.9 < \kappa_{\mathrm{t}} < -0.8$ and $0.9 < \kappa_{\mathrm{t}} < 1.1$ at 95% confidence level, assuming the rest of the couplings to be those of the SM.