Search For Charged Higgs Bosons Decaying To Top And Bottom Quarks In Proton Antiproton Collisions PDF Download

The Standard Model predicts the existence of one neutral scalar Higgs boson, which is a remnant of the mechanism that breaks the SU(2)[sub L]xU(1)[sub Y] electroweak symmetry and generates masses for the heavy vector bosons and fermions. Many extensions to the Standard Model predict two or more Higgs doublets, resulting in a larger spectrum of Higgs bosons including a charged Higgs boson (H[sup [+-]]). For a light charged Higgs boson mass, the top decay into a charged Higgs boson and bottom quark might occur. This thesis presents results of a direct search for this top quark decay mode via the charged Higgs decay to a tau lepton and tau-neutrino, using the hadronic decays of the tau leptons. The search data consist of 100 pb[sup -1] of Run 1 data collected between 1992-1995 at the CDF detector, from p[anti p] collisions at a center-of-mass energy of 1.8 TeV produced at Fermilab's Tevatron accelerator. A total of seven events are observed in two search channels with an expected background contribution of 7.4[+-]2.0 events coming from fake taus (5.4[+-]1.5), heavy vector boson decays with jets (1.9[+-]1.3) and dibosons(0.08[+-]0.06). Lacking evidence for a signal, we set limits on charged Higgs production at the 95% confidence level in the charged Higgs mass plane versus tan[beta](a parameter of the theory) for a top quark mass of 175 GeV/c[sup 2] and for top production cross sections ([sigma][sub t[anti t]]) of 5.0 and 7.5 pb, assuming the Type-II Two-Higgs-Doublet-Model. For large tan[beta], this analysis excludes a charged Higgs boson of mass below 147(158)GeV/c[sup 2] for [sigma][sub t[anti t]]=5.0(7.5)pb. Using the Standard Model measured top quark cross section from CDF, this limit increases to 168 GeV/c[sup 2] and we also exclude a branching fraction of top decays via this charged Higgs mode of greater than 43% for charged Higgs masses below 168 GeV/c[sup 2].