Study of Top-Quark Production and Decays involving a Tau Lepton at CDF and Limits on a Charged-Higgs Boson Contribution

Abstract

We present an analysis of top-antitop quark production and decay into a tau lepton, tau neutrino, and bottom quark using data from $9{\mathrm{fb}}^{-1}$ of integrated luminosity at the Collider Detector at Fermilab. Dilepton events, where one lepton is an energetic electron or muon and the other a hadronically-decaying tau lepton, originating from proton-antiproton collisions at $\sqrt{s}=1.96TeV$ are used. A top-antitop quark production cross section of $8.1\pm 2.1\mathrm{pb}$ is measured, assuming standard-model top-quark decays. By separately identifying for the first time the single-tau and the ditau components, we measure the branching fraction of the top quark into tau lepton, tau neutrino, and bottom quark to be $(9.6\pm 2.8)$. The branching fraction of top-quark decays into a charged Higgs boson and a bottom quark, which would imply violation of lepton universality, is limited to be less than $5.9$ at $95$ confidence level.

8 pages, 5 figures accepted by Phys. Rev. D

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