This thesis describes a search for the Higgs boson, a new particle predicted by a theory called the minimal supersymmetric extension to the standard model (MSSM). The standard model of particle physics, the MSSM, and Higgs boson phenomenology are introduced briefly. The search presented in this thesis uses a single final state configuration, in which the Higgs boson decays to two tau leptons, with one tau decaying to a muon and neutrinos, and the other decaying to pions and a single neutrino. Two new methods are introduced in this analysis, the Tau Neural Classifier tau identification algorithm, and the Secondary Vertex fit tau pair mass reconstruction method. Both methods are discussed in detail. The analysis uses the 2010 dataset from the Compact Muon Solenoid (CMS) experiment, which contains 36 pb−1 of integrated luminosity at a center of mass energy of 7 TeV. In total, 573 events are selected in the analysis. We fit the observed tau pair mass spectrum and measure the composition of the events. The result is compatible with the standard model expectation. No excess of signal events is observed, and we set an upper limit on the cross section times branching ratio of a Higgs boson. This limit is interpreted in the parameter space of the MSSM.

A search for neutral Higgs bosons in the minimal supersymmetric extension of the standard model (MSSM) decaying to tau-lepton pairs in pp collisions is performed, using events recorded by the CMS experiment at the LHC. The dataset corresponds to an integrated luminosity of 24.6 fb−1, with 4.9 fb−1 at 7 TeV and 19.7 fb−1 at 8 TeV. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes the case where the Higgs boson is produced in association with a b-quark jet. No excess is observed in the tau-lepton-pair invariant mass spectrum. Exclusion limits are presented in the MSSM parameter space for different benchmark scenarios, mhmax, mhmod+, mhmod-, light-stop, light-stau, [tau]-phobic, and low-mH. Upper limits on the cross section times branching fraction for gluon fusion and b-quark associated Higgs boson production are also given.

A search for neutral MSSM Higgs bosons in pp collisions at the LHC at a center-of-mass energy of 7 TeV is presented. The results are based on a data sample corresponding to an integrated luminosity of 36 inverse picobarns recorded by the CMS experiment. The search uses decays of the Higgs bosons to tau pairs. No excess is observed in the tau-pair invariant-mass spectrum. The resulting upper limits on the Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, yield stringent new bounds in the MSSM parameter space.

We report results from a search for neutral Higgs bosons produced in association with b quarks using data recorded by the D0 experiment at the Fermilab Tevatron Collider and corresponding to an integrated luminosity of 7.3 fb−1. This production mode can be enhanced in several extensions of the standard model (SM) such as in its minimal supersymmetric extension (MSSM) at high tan [beta]. We search for Higgs bosons decaying to tau pairs with one tau decaying to a muon and neutrinos and the other to hadrons. The data are found to be consistent with SM expectations, and we set upper limits on the cross section times branching ratio in the Higgs boson mass range from 90 to 320 GeV/c2. We interpret our result in the MSSM parameter space, excluding tan [beta] values down to 25 for Higgs boson masses below 170 GeV/c2.

The work presented in this thesis spans a wide range of experimental particle physics subjects, starting from level-1 trigger electronics to the final results of the search for Higgs boson decay and to tau lepton pairs. The thesis describes an innovative reconstruction algorithm for tau decays and details how it was instrumental in providing a measurement of Z decay to tau lepton pairs. The reliability of the analysis is fully established by this measurement before the Higgs boson decay to tau lepton pairs is considered. The work described here continues to serve as a model for analysing CMS Higgs to tau leptons measurements.