| Zusammenfassung: | The work presented in this thesis comprises two analyses performed using 13 TeV proton-proton collision data recorded in the years 2016 to 2018 with the CMS detector at the LHC. The dataset analysed corresponds to an integrated luminosity of about 137fb−1. First, the calibration of the jet transverse momentum resolution is described, and second, the search for heavy resonances decaying to a Z and ... The work presented in this thesis comprises two analyses performed using 13 TeV proton-proton collision data recorded in the years 2016 to 2018 with the CMS detector at the LHC. The dataset analysed corresponds to an integrated luminosity of about 137fb−1. First, the calibration of the jet transverse momentum resolution is described, and second, the search for heavy resonances decaying to a Z and Higgs boson is presented.
In the first part of this work, the technique for the calibration of the jet transverse momentum resolution adopted in the CMS Collaboration is described in detail. The method exploits QCD dijet events to calibrate the width of the jet response distribution in simulated events to match the one in data. A wide range in jet transverse momentum ranging from 100GeV to 1TeV is covered up to a pseudorapidity of |η| = 5.2. The uncertainties of the results obtained are improved by up to a factor of 3 compared to the previous measurement. In particular, a thorough statistical treatment of the systematic uncertainties leads to an enhanced calibration precision. The results derived with dijet events are combined for the first time with those obtained in Z+jet topologies, allowing the extension down to transverse momenta of 40 GeV.
In the second part of this work, a search for the resonant production of a hypo- thetical spin-1 massive particle decaying into a Z and a Higgs boson is presented. Predicted by a multitude of theories, such diboson resonances are promising particles to resolve several shortcomings of the Standard Model. The analysis is carried out in the final state with two electrons or muons and a large-radius jet, identified as originating from the hadronic decays of a Higgs boson. In particular, the 4-prong (H → qqqq) and c flavour (H → cc) decays are targeted for the first time in this context. Recent advances in machine learning-based jet tagging algorithms are exploited to maximise the sensitivity of this search. A full statistical combination with an analysis targeting invisible Z boson decays is performed within the context of this thesis. No excess over the Standard Model expectation is observed and upper limits on the production cross section of the resonance are placed. Resonances decaying exclusively into a Z and a Higgs boson are excluded below masses of 2.45 and 2.72 TeV, depending on the theoretical model under consideration. The results obtained show a sensitivity to high resonance masses that exceeds that of the H → bb channel despite its much larger branching fraction. |
