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Abstract:

In this paper we report a measurement of the tt̄ production cross section in pp̄ collisions at √s=1.96TeV using data corresponding to an integrated luminosity of 2.2fb-1 collected with the CDF II detector at the Tevatron accelerator. We select events with significant missing transverse energy and high jet multiplicity. This measurement vetoes the presence of explicitly identified electrons and muons, thus enhancing the tau contribution of tt̄ decays. Signal events are discriminated from the background using a neural network, and heavy flavor jets are identified by a secondary-vertex tagging algorithm. We measure a tt̄ production cross section of 7.99±0.55(stat)±0.76(syst)±0.46(lumi) pb, assuming a top mass mtop=172.5GeV/c2, in agreement with previous measurements and standard model predictions. © 2011 American Physical Society.

Abstract:

We present a new method to measure the top quark pair production cross section and the background rates with data corresponding to an integrated luminosity of 2.7fb-1 from pp̄ collisions at √s=1.96TeV collected with the CDF II Detector. We select events with a single electron or muon candidate, missing transverse energy, and at least one b-tagged jet. We perform a simultaneous fit to a jet flavor discriminant across nine samples defined by the number of jets and b tags. An advantage of this approach is that many systematic uncertainties are measured in situ and inversely scale with integrated luminosity. We measure a top cross section of σ tt̄=7.64±0.57(stat+syst)±0.45(luminosity)pb. © 2011 American Physical Society.

Abstract:

Using Zγ candidate events collected by the CDF detector at the Tevatron Collider, we search for potential anomalous (non-standard-model) couplings between the Z boson and the photon. Zγ couplings vanish at tree level and are heavily suppressed at higher orders; hence any evidence of couplings indicates new physics. Measurements are performed using data corresponding to an integrated luminosity of 4.9fb-1 in the Z→νν̄ decay channel and 5.1fb-1 in the Z→l +l- (l=μ, e) decay channels. The combination of these measurements provides the most stringent limits to date on Zγ trilinear gauge couplings. Using an energy scale of Λ=1.5TeV to allow for a direct comparison with previous measurements, we find limits on the CP-conserving parameters that describe Zγ couplings to be |h3γ,Z|<0.022 and |h4γ,Z|<0.0009. These results are consistent with standard model predictions. © 2011 American Physical Society.

Abstract:

A search for new dielectron-mass resonances using data recorded by the CDF II detector and corresponding to an integrated luminosity of 5.7fb-1 is presented. No significant excess over the expected standard model prediction is observed. In this data set, an event with the highest dielectron mass ever observed (960GeV/c2) was recorded. The results are interpreted in the Randall-Sundrum (RS) model. Combined with the 5.4fb-1 diphoton analysis, the RS-graviton lower-mass limit for the coupling k/M ̄Pl=0.1 is 1058GeV/c2, making it the strongest limit to date. © 2011 American Physical Society.

Abstract:

We present the first model independent search for three-jet hadronic resonances within multijet events in √s=1.96TeV pp̄ collisions at the Fermilab Tevatron using the CDF II detector. Pair production of supersymmetric gluinos and squarks with hadronic R-parity violating decays is employed as an example of a new physics benchmark for this signature. Selection criteria based on the kinematic properties of an ensemble of jet combinations within each event help to extract signal from copious QCD background. No significant excess outside the top quark mass window is observed in data with an integrated luminosity of 3.2fb⊃-1. We place 95% confidence level limits on the production cross section σ(pp̄→XX⊃′) ×BR(gg→3jet+3jet) where X, X⊃′=g, q, or q̄, with q, q̄→g+jet, as a function of gluino mass, in the range of 77GeV/c2 to 240GeV/c2. © 2011 American Physical Society.