Search for new color-octet vector particle decaying to tT{topbar} in pP{topbar} collisions at √s=1.96 TeV
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 691:4 (2010) 183-190
Abstract:
We present the result of a search for a massive color-octet vector particle, (e.g. a massive gluon) decaying to a pair of top quarks in proton-antiproton collisions with a center-of-mass energy of 1.96 TeV. This search is based on 1.9 fb-1 of data collected using the CDF detector during Run II of the Tevatron at Fermilab. We study tT{topbar} events in the lepton. +. jets channel with at least one b-tagged jet. A massive gluon is characterized by its mass, decay width, and the strength of its coupling to quarks. These parameters are determined according to the observed invariant mass distribution of top quark pairs. We set limits on the massive gluon coupling strength for masses between 400 and 800 GeV/c2 and width-to-mass ratios between 0.05 and 0.50. The coupling strength of the hypothetical massive gluon to quarks is consistent with zero within the explored parameter space. © 2010 Elsevier B.V.Measurement of W-boson polarization in Top-Quark Decay in pp collisions at sqrt[s]=1.96 TeV.
Phys Rev Lett 105:4 (2010) 042002
Abstract:
We report measurements of the polarization of W bosons from top-quark decays using 2.7 fb{-1} of pp collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c{2}, three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f{0}) and right-handed (f{+}) W bosons yields the model-independent results f{0}=0.88±0.11(stat)±0.06(syst) and f{+}=-0.15±0.07(stat)±0.06(syst) with a correlation coefficient of -0.59. A measurement of f{0} [f{+}] constraining f{+} [f{0}] to its standard model value of 0.0 [0.7] yields f{0}=0.70±0.07(stat)±0.04(syst) [f{+}=-0.01±0.02(stat)±0.05(syst)]. All these results are consistent with standard model expectations. We achieve the single most precise measurements of f{0} for both the model-independent and model-dependent determinations.Combined Tevatron upper limit on gg→H→W+W- and constraints on the Higgs boson mass in fourth-generation fermion models
Physical Review D - Particles, Fields, Gravitation and Cosmology 82:1 (2010)
Abstract:
We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg→H→W+W - in pp̄ collisions at the Fermilab Tevatron Collider at √s=1.96TeV. With 4.8fb-1 of integrated luminosity analyzed at CDF and 5.4fb-1 at D0, the 95% confidence level upper limit on σ(gg→H)×B(H→W+W-) is 1.75 pb at mH=120GeV, 0.38 pb at mH=165GeV, and 0.83 pb at mH=200GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV. © 2010 The American Physical Society.Measurement of the ratio σ{tt}/σ{Z/γ{*}→ll} and precise extraction of the tt cross section.
Phys Rev Lett 105:1 (2010) 012001
Abstract:
We report a measurement of the ratio of the tt to Z/γ{*} production cross sections in sqrt[s]=1.96 TeV pp collisions using data corresponding to an integrated luminosity of up to 4.6 fb{-1}, collected by the CDF II detector. The tt cross section ratio is measured using two complementary methods, a b-jet tagging measurement and a topological approach. By multiplying the ratios by the well-known theoretical Z/γ{*}→ll cross section predicted by the standard model, the extracted tt cross sections are effectively insensitive to the uncertainty on luminosity. A best linear unbiased estimate is used to combine both measurements with the result σ{tt}=7.70±0.52 pb, for a top-quark mass of 172.5 GeV/c{2}.Erratum: Measurement of the W+W- production cross section and search for anomalous WWγ and WWZ couplings in pp̄ collisions at √s=1.96 TeV (Phys. Rev. Lett. (2010) 104 (201801))
Physical Review Letters 105:1 (2010)