We report a measurement of single top quark production in proton-antiproton collisions at a center-of-mass energy of sqrt{s} = 1.96 TeV using a data set corresponding to 7.5 fb-1 of integrated luminosity collected by the Collider Detector at Fermilab
. We select events consistent with the single top quark decay process t to Wb to l{ u}b by requiring the presence of an electron or muon, a large imbalance of transverse momentum indicating the presence of a neutrino, and two or three jets including at least one originating from a bottom quark. An artificial neural network is used to discriminate the signal from backgrounds. We measure a single top quark production cross section of 3.04+0.57-0.53 pb and set a lower limit on the magnitude of the coupling between the top quark and bottom quark |Vtb| > 0.78 at the 95% credibility level.
A search for forbidden and exotic Z boson decays in the diphoton mass spectrum is presented for the first time in hadron collisions, based on data corresponding to 10.0 fb^-1 of integrated luminosity from proton-antiproton collisions at sqrt(s) = 1.9
6 TeV collected by the CDF experiment. No evidence of signal is observed, and 95% credibility level Bayesian upper limits are set on the branching ratios of decays of the Z boson to a photon and neutral pion (which is detected as a photon), a pair of photons, and a pair of neutral pions. The observed branching ratio limits are 2.01 x 10^-5 for Z to pi^0gamma, 1.46 x 10^-5 for Z to gammagamma, and 1.52 x 10^-5 for Z to pi^0pi^0. The Z to pi^0gamma and Z to gammagamma limits improve by factors of 2.6 and 3.6, respectively, the most stringent results from other experiments. The Z to pi^0pi^0 branching ratio limit is the first experimental result on this decay.
A search for a narrow Higgs boson resonance in the diphoton mass spectrum is presented based on data corresponding to 7.0 fb^-1 of integrated luminosity from p-pbar collisions at sqrt(s) = 1.96 TeV collected by the CDF experiment. No evidence of such
a resonance is observed, and upper limits are set on the cross section times branching ratio of the resonant state as a function of Higgs boson mass. The limits are interpreted in the context of the standard model and one fermiophobic benchmark model where the data exclude fermiophobic Higgs bosons with masses below 114 GeV/c^2 at a 95% Bayesian credibility level.
