Precise jet measurements and search for Supersymmetry particles

Searches for physics beyond Standard Model (SM) are one of the main goals of the CMSexperiment at the Large Hadron Collider (LHC). Among the investigated theories is Supersymmetry (SUSY), which would manifest in a production of new particles. As theLHC is a hadron collider, it is expected that colored SUSY particles would be producedin abundance if they were light enough. The decays of these new particles would manifestin a production of jets. A good understanding of the properties of the jets is crucial tointerpret searches targeting such scenarios.In this thesis, the measurement of the jet energy resolution in data and in simulation,and a search for supersymmetry in multijet events with missing transverse momentum arepresented.The measurement of the jet energy resolution was performed on data collected at the√center of mass energy of s = 13 TeV at the CMS experiment in 2016. The methodemployed uses the balance of the transverse momentum in dijet events to compute thedata to simulation ratios of the jet energy resolution, which are used as a correction factorin simulation. Furthermore, similar scale factors are calculated for the non-gaussian partof the jet response.A search for supersymmetry in events with jets and missing transverse momentum is performed on the same data as the measurement of the jet energy resolution. The main focusof the work presented in this thesis was the estimation of the background arising fromQCD multijet events. The method, that was used, called rebalance and smear, predictsthe QCD contribution to the SM backgrounds based on a jet resolution model.The observed number of events agree with the Standard Model background predictionsand no evidence for supersymmetry has been observed. The upper limit on the production cross sections and exclusion curves for SUSY particles for different simplified models(SMs) are calculated. The production of gluinos with masses in a range of 1800-1960 GeVwere excluded for masses of the lightest supersymmetric particle (LSP)up to values of 1TeV for different simplified models at 95% confidence level. The top, bottom and lightsquarks with masses below 960, 1050 and 1450 GeV, respectively, were also excluded formasses of LSP below 400 GeV for the considered simplified models.