A combined search for the standard model Higgs boson at sqrt(s) = 1.96 TeV
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 663:1-2 (2008) 26-36
Abstract:
We present new results of the search for W H → ℓ ν b over(b, ̄) production in p over(p, ̄) collisions at a center-of-mass energy of sqrt(s) = 1.96 TeV, based on a dataset with integrated luminosity of 0.44 fb-1. We combine these new results with previously published searches by the D0 collaboration, for WH and ZH production analyzed in the E{combining long solidus overlay}T b over(b, ̄) final state, for ZH (→ ℓ+ ℓ- b over(b, ̄)) production, for WH (→ W W W) production, and for H (→ W W) direct production. No signal-like excess is observed either in the WH analysis or in the combination of all D0 Higgs boson analyses. We set 95% C.L. (expected) upper limits on σ (p over(p, ̄) → W H) × B (H → b over(b, ̄)) ranging from 1.6 (2.2) pb to 1.9 (3.3) pb for Higgs boson masses between 105 and 145 GeV, to be compared to the theoretical prediction of 0.13 pb for a Standard Model (SM) Higgs boson with mass mH = 115 GeV. After combination with the other D0 Higgs boson searches, we obtain for mH = 115 GeV an observed (expected) limit 8.5 (12.1) times higher than the SM predicted Higgs boson production cross section. For mH = 160 GeV, the corresponding observed (expected) ratio is 10.2 (9.0). © 2008 Elsevier B.V.Measurement of the tt̄ production cross section in pp̄ collisions at s=1.96TeV
Physical Review Letters 100:19 (2008)
Abstract:
We measure the tt̄ production cross section in pp̄ collisions at s=1.96TeV in the lepton+jets channel. Two complementary methods discriminate between signal and background: b tagging and a kinematic likelihood discriminant. Based on 0.9fb-1 of data collected by the D0 detector at the Fermilab Tevatron Collider, we measure σtt̄=7.62±0.85pb, assuming the current world average mt=172.6GeV. We compare our cross section measurement with theory predictions to determine a value for the top-quark mass of 170±7GeV. © 2008 The American Physical Society.Simultaneous Measurement of the Ratio R=B(t→Wb)/B(t→Wq) and the Top-Quark Pair Production Cross Section with the D0 Detector at s=1.96TeV
Physical Review Letters 100:19 (2008)
Abstract:
We present the first simultaneous measurement of the ratio of branching fractions, R=B(t→Wb)/B(t→Wq), with q being a d, s, or b quark, and the top-quark pair production cross section σtt̄ in the lepton plus jets channel using 0.9fb-1 of pp̄ collision data at s=1.96TeV collected with the D0 detector. We extract R and σtt̄ by analyzing samples of events with 0, 1, and 2 identified b jets. We measure R=0.97-0.08+0.09(stat+syst) and σtt̄=8.18-0.84+0.90(stat+syst)±0.50(lumi)pb, in agreement with the standard model prediction. © 2008 The American Physical Society.Search for excited electrons in pp̄ collisions at s=1.96TeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 77:9 (2008)
Abstract:
We present the results of a search for the production of an excited state of the electron, e*, in proton-antiproton collisions at s=1.96TeV. The data were collected with the D0 experiment at the Fermilab Tevatron Collider and correspond to an integrated luminosity of approximately 1fb-1. We search for e* in the process pp̄→e*e, with the e* subsequently decaying to an electron plus photon. No excess above the standard model background is observed. Interpreting our data in the context of a model that describes e* production by four-fermion contact interactions and e* decay via electroweak processes, we set 95% C.L. upper limits on the production cross section ranging from 8.9 to 27 fb, depending on the mass of the excited electron. Choosing the scale for contact interactions to be Λ=1TeV, excited electron masses below 756 GeV are excluded at the 95% C.L. © 2008 The American Physical Society.Measurement of the forward-backward charge asymmetry in top-quark pair production.
Phys Rev Lett 100:14 (2008) 142002