Jeff Tseng

Abstract:

We report on a search for anomalous kinematics of tt̄ dilepton events in pp̄ collisions at s=1.96TeV using 193pb-1 of data collected with the CDF II detector. We developed a new a priori technique designed to isolate the subset in a data sample revealing the largest deviation from standard model (SM) expectations and to quantify the significance of this departure. In the four-variable space considered, no particular subset shows a significant discrepancy, and we find that the probability of obtaining a data sample less consistent with the SM than what is observed is 1.0%-4.5%. © 2005 The American Physical Society.

Abstract:

We present a measurement of the W+W- production cross section using 184pb-1 of pp̄ collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W+W-→ℓ+νℓ-ν̄, where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0-0.8+2.2 events. The resulting W+W- production cross-section measurement of σ(pp̄→W+W-)=14.6-5.1+5.8(stat)-3.0+1.8(syst) ±0.9(lum)pb agrees well with the standard model expectation. © 2005 The American Physical Society.

Abstract:

We report the first largely model independent measurement of charged particle multiplicities in quark and gluon jets, Nq and Ng, produced at the Fermilab Tevatron in pp collisions with a center-of-mass energy of 1.8 TeV and recorded by the Collider Detector at Fermilab. The measurements are made for jets with average energies of 41 and 53 GeV by counting charged particle tracks in cones with opening angles of θc = 0:28, 0.36, and 0.47 rad around the jet axis. The corresponding jet hardness Q = Ejetθc varies in the range from 12 to 25 GeV. At Q = 19:2 GeV, the ratio of multiplicities r = Ng=Nq is found to be 1:64 ± 0:17, where statistical and systematic uncertainties are added in quadrature. The results are in agreement with resummed perturbative QCD calculations.

Abstract:

We present a search for ZZ and ZW vector boson pair production in pp̄ collisions at s=1.96TeV using the leptonic decay channels ZZ→llνν, ZZ→lll′l′, and ZW→lll′ν. In a data sample corresponding to an integrated luminosity of 194pb-1 collected with the Collider Detector at Fermilab, 3 candidate events are found with an expected background of 1.0±0.2 events. We set a 95% confidence level upper limit of 15.2pb on the cross section for ZZ plus ZW production, compared to the standard model prediction of 5.0±0.4pb. © 2005 The American Physical Society.

Abstract:

We report a measurement of the tt̄ production cross section using the CDF II detector at the Fermilab Tevatron. The data consist of events with an energetic electron or muon, missing transverse energy, and three or more hadronic jets, at least one of which is identified as a b-quark jet by reconstructing a secondary vertex. The background fraction is determined from a fit of the transverse energy of the leading jet. Using 162 ± 10 pb ^-1 of data, the total cross section is found to be 6.0 ± 1.6(stat.) ± 1.2(syst.) pb, which is consistent with the standard model prediction. © 2005 The American Physical Society.