Heindl, Maximilian. Inclusive search for new nonresonant phenomena in multilepton final states with the CMS detector at the LHC. Retrieved from https://doi.org/doi:10.7282/t3-4nvv-vj02
DescriptionMany theories of physics beyond the Standard Model, such as the type-III seesaw mechanism, vector-like taus, or third generation scalar leptoquarks, can be probed at the Large Hadron Collider (LHC) by searching for signatures with multiple leptons. Therefore, an inclusive search for nonresonant signatures of phenomena beyond the Standard Model in events with three or more charged leptons (electrons, muons, and hadronic taus) is performed and presented in this dissertation. The data sample corresponds to a total integrated luminosity of 138 inverse fb recorded in proton-proton collisions at 13 TeV by the CMS experiment at the LHC in 2016–2018. A signal model independent event categorization scheme is developed to probe multiple scenarios of the above-mentioned signal models. This scheme is based on the lepton charge and flavor multiplicities, invariant masses of lepton pairs, as well as on the multiplicity of b quark jets, and various kinematic variables. In the absence of any significant deviation from the background expectations, lower limits are set on the masses of type-III seesaw heavy fermions at 740 GeV for any branching fraction scenario to Standard Model leptons. Similarly, vector-like taus are excluded for masses below 920 GeV for the doublet model, and in the mass range of 120–180 GeV for the singlet model. In addition, scalar leptoquarks decaying exclusively to a top quark and a charged lepton of any flavor are excluded for masses below 1230 GeV.