A Search for Additional Neutral Higgs Bosons in $\tau\tau$ Final States in pp Collisions at $\sqrt{s} = 13\, \mathrm{TeV}$

Many proposed extensions of the standard model of particle physics (SM) predict an extended Higgs sector with respect to the SM. Experimentally, this extended Higgs sector is accessible through searches for additional spin-0 particles often referred to as additional Higgs bosons. Decays of neutral Higgs bosons to pairs of tau leptons provide the prime search channel for such particles in the minimal supersymmetric SM (MSSM) and other two-Higgs-doublet models (2HDM) of Type II since their couplings are enhanced in wide areas of the parameter space. In this thesis, a search for such decays in the form of a search for an additional resonance above the SM prediction in the $\tau\tau$ mass spectrum, targeting the production via gluon fusion and in association with b quarks, is presented. The results are portrayed in two ways. First, model-independent exclusion limits on the product of the production cross section and the branching fraction for the decay into tau leptons of the targeted resonance are derived. These limits translate into model-dependent exclusion contours in a set of MSSM and 2HDM benchmark scenarios, which are inferred from the full $\tau\tau$ spectrum predicted by the investigated scenario.