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Abstract:

This article presents a measurement of the top quark mass using the CDF II detector at Fermilab. Colliding beams of protons and antiprotons at Fermilab's Tevatron (s=1.96TeV) produce top/antitop pairs, which decay to W+W-bb̄; events are selected where one W decays to hadrons and the other W decays to either e or μ plus a neutrino. The data sample corresponds to an integrated luminosity of approximately 318pb-1. A total of 165 tt̄ events are separated into four subsamples based on jet transverse energy thresholds and the number of b jets identified by reconstructing a displaced vertex. In each event, the reconstructed top quark invariant mass is determined by minimizing a χ2 for the overconstrained kinematic system. At the same time, the mass of the hadronically decaying W boson is measured in the same event sample. The observed W boson mass provides an in situ improvement in the determination of the hadronic jet energy scale. A simultaneous likelihood fit of the reconstructed top quark masses and the W boson invariant masses in the data sample to distributions from simulated signal and background events gives a top quark mass of 173.5-3.8+3.9GeV/c2. © 2006 The American Physical Society.

Abstract:

We report two measurements of the top-quark mass Mtop using the CDF II detector at the Fermilab Tevatron in a 318pb-1 data sample of tt̄ events in the lepton+jets final state. One method uses an event-based likelihood technique resulting in Mtop=173.2-2.4+2.6(stat)±3.2(syst)GeV/c2 or 173.2-4.0+4.1GeV/c2. The second method reconstructs a top-quark mass in each event using the measured invariant mass of the hadronically decaying W boson to constrain the jet energy scale to obtain a value for Mtop of 173.5-3.6+3.7(stat)±1.3(syst)GeV/c2 or 173.5-3.8+3.9GeV/c2. We take the latter, which is more precise, as our result. © 2006 The American Physical Society.

Abstract:

We present a search for neutral supersymmetric Higgs bosons decaying to τ pairs produced in pp̄ collisions at s=1.96TeV. The data, corresponding to 310pb-1 integrated luminosity, were collected with the Collider Detector at Fermilab in runII of the Tevatron. No significant excess above the standard model backgrounds is observed. We set exclusion limits on the production cross section times branching fraction to τ pairs for Higgs boson masses in the range from 90 to 250GeV/c2. © 2006 The American Physical Society.

Abstract:

We search for pair-produced Dirac magnetic monopoles in 35.7pb-1 of proton-antiproton collisions at s=1.96TeV with the Collider Detector at Fermilab (CDF). We find no monopole candidates corresponding to a 95% confidence-level cross-section limit σ<0.2pb for a monopole with mass between 200 and 700GeV/c2. Assuming a Drell-Yan pair-production mechanism, we set a mass limit m>360GeV/c2. © 2006 The American Physical Society.

Abstract:

We report the first evidence for a fully reconstructed decay mode of the Bc± meson in the channel Bc±→J/ψπ±, with J/ψ→μ+μ-. The analysis is based on an integrated luminosity of 360pb-1 in pp̄ collisions at 1.96 TeV center of mass energy collected by the Collider Detector at Fermilab. We observe 14.6±4.6 signal events with a background of 7.1±0.9 events, and a fit to the J/ψπ± mass spectrum yields a Bc± mass of 6285.7±5.3(stat)±1. 2(syst)MeV/c2. The probability of a peak of this magnitude occurring by random fluctuation in the search region is estimated as 0.012%. © 2006 The American Physical Society.