Professor Daniela Bortoletto

Abstract:

We present a measurement of the tt̄ production cross section in pp̄ collisions at s=1.96TeV which uses events with an inclusive signature of significant missing transverse energy and jets. This is the first measurement which makes no explicit lepton identification requirements, so that sensitivity to W→τν decays is maintained. Heavy flavor jets from top quark decay are identified with a secondary vertex tagging algorithm. From 311pb-1 of data collected by the Collider Detector at Fermilab, we measure a production cross section of 5.8±1.2(stat)-0.7+0.9(syst)pb for a top quark mass of 178GeV/c2, in agreement with previous determinations and standard model predictions. © 2006 The American Physical Society.

Abstract:

We report the observation of Bs ⁰- B̄s ⁰ oscillations from a time-dependent measurement of the Bs ⁰-B̄s ⁰ oscillation frequency Δms. Using a data sample of 1 fb^-1 of pp collisions at √ = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron, we find signals of 5600 fully reconstructed hadronic B s decays, 3100 partially reconstructed hadronic Bs decays, and 61500 partially reconstructed semileptonic Bs decays. We measure the probability as a function of proper decay time that the Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal for Bs ⁰-B̄s ⁰ oscillations. The probability that random fluctuations could produce a comparable signal is 8 × 10^-8, which exceeds 5σ significance. We measure Δms = 17.77 ± 0.10(stat) ± 0.07(syst) ps^-1 and extract |Vtd/Vts| = 0.2060 ± 0.0007(Δms)-0.0060 ^+0.0081 (Δmd + theor). © 2006 The American Physical Society.

Abstract:

We present a study of the dijet invariant mass distribution for the reaction p̄p→twojets+γ+X, at a center of mass energy of 1.8 TeV, using data collected by the CDF experiment. We compare the data to predictions for the production of a photon with two jets, together with the resonant processes p̄p→W/Z+γ+X, in which the W and Z bosons decay hadronically. A fit is made to the dijet invariant mass distribution combining the nonresonant background and resonant processes. We use the result to establish a limit for the inclusive production cross section of W/Z+γ with hadronic decay of the W and Z bosons. © 2006 The American Physical Society.

Abstract:

We report the results of a search for a charged Higgs boson in the decays of top quarks produced in pp̄ collisions at a center-of-mass energy of 1.96 TeV. We use a data sample corresponding to an integrated luminosity of 193pb-1 collected by the upgraded Collider Detector at Fermilab. No evidence for charged Higgs production is found, allowing 95% C.L. upper limits to be placed on BR(t→H+b) for different charged Higgs decay scenarios. In addition, we present in the minimal supersymmetric standard model (mH±,tan β) plane the first exclusion regions with radiative and Yukawa coupling corrections. © 2006 The American Physical Society.