Studying the underlying event in Drell-Yan and high transverse momentum jet production at the Tevatron
Physical Review D - Particles, Fields, Gravitation and Cosmology 82:3 (2010)
Abstract:
We study the underlying event in proton-antiproton collisions by examining the behavior of charged particles produced in association with a large transverse momentum jet (∼2.2fb-1) or with a Drell-Yan lepton pair (∼2.7fb-1) in the Z-boson mass region [70Search 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.First measurement of Bose-Einstein correlations in proton-proton collisions at √s=0.9 and 2.36 TeV at the LHC
Physical Review Letters 105:3 (2010)