| 11. |
- Abazov, V. M., et al.
(författare)
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Measurement of the top quark pair production cross section in the lepton plus jets channel in proton-antiproton collisions at root s=1.96 TeV
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:1, s. 012008-
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the inclusive top quark pair production cross section in p (p) over bar collisions at root s = 1.96 TeV utilizing data corresponding to an integrated luminosity of 5.3 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing one high-p(T) isolated electron or muon and at least two jets, and we perform three analyses: one exploiting specific kinematic features of t (t) over bar events, the second using b-jet identification, and the third using both techniques to separate the t (t) over bar signal from the background. In the third case, we determine simultaneously the t (t) over bar cross section and the ratio of the production rates of W + heavy flavor jets and W + light flavor jets, which reduces the impact of the systematic uncertainties related to the background estimation. Assuming a top quark mass of 172.5 GeV, we obtain sigma(t (t) over bar) = 7.78(-0.64)(-0.77)pb. This result agrees with predictions of the standard model.
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| 12. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the W boson helicity in top quark decays using 5.4 fb(-1) of p(p)over-bar collision data
- 2011
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Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 83:3, s. 032009-
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the helicity of the W boson produced in top quark decays using t (t) over bar decays in the l + jets and dilepton final states selected from a sample of 5.4 fb(-1) of collisions recorded using the D0 detector at the Fermilab Tevatron p (p) over bar collider. We measure the fractions of longitudinal and right-handed W bosons to be f(0) = 0.669 +/- 0.102[+/- 0.078(stat.) +/- 0.065(syst.) +/- and f(+) = 0.023 +/- 0.053[+/- 0.041(stat.) +/- 0.034(syst.)], respectively. This result is consistent at the 98% level with the standard model. A measurement with f(0) fixed to the value from the standard model yields f(+) = 0.010 +/- 0.037[+/- 0.022(stat.) +/- 0.030(syst.).].
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| 13. |
- Abazov, V. M., et al.
(författare)
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Model-independent measurement of t-channel single top quark production in p(p)over-bar collisions at,root s=1.96 TeV
- 2011
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 705:4, s. 313-319
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Tidskriftsartikel (refereegranskat)abstract
- We present a model-independent measurement of t-channel electroweak production of single top quarks in p collisions at root s = 1.96 TeV. Using 5.4 fb(-1) of integrated luminosity collected by the DO detector at the Fermilab Tevatron Collider, and selecting events containing an isolated electron or muon, missing transverse energy and one or two jets originating from the fragmentation of b quarks, we measure a cross section sigma (p (p) over bar -> tqb + X) = 2.90 +/- 0.59 (stat + syst) pb for a top quark mass of 172.5 GeV. The probability of the background to fluctuate and produce a signal as large as the one observed is 1.6 x 10(-8), corresponding to a significance of 5.5 standard deviations. (C) 2011 Elsevier B.V. All rights reserved.
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| 14. |
- Abazov, V. M., et al.
(författare)
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Search for the Standard Model Higgs Boson in the H -> WW -> lvq '(q)over-bar Decay Channel
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:17, s. 171802-
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Tidskriftsartikel (refereegranskat)abstract
- We present a search for the standard model Higgs boson (H) in p (p) over bar collisions at root s = 1.96 TeV in events containing a charged lepton (l), missing transverse energy, and at least two jets, using 5.4 fb(-1) of integrated luminosity recorded with the D0 detector at the Fermilab Tevatron Collider. This analysis is sensitive primarily to Higgs bosons produced through the fusion of two gluons or two electroweak bosons, with subsequent decay H -> WW -> lvq'(q) over bar, where l is an electron or muon. The search is also sensitive to contributions from other production channels, such as WH -> lvb (b) over bar. In the absence of a signal, we set limits at the 95% C.L. on the cross section for H production sigma(p (p) over bar -> H + X) in these final states. For a mass of M-H = 160 GeV, the limit is a factor of 3.9 larger than the cross section in the standard model and consistent with an a priori expected sensitivity of 5.0.
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| 15. |
- Abazov, V. M., et al.
(författare)
-
Search for W H associated production in 5.3 fb(-1) of p(p)over-bar collisions at the Fermilab Tevatron
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 698:1, s. 6-13
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Tidskriftsartikel (refereegranskat)abstract
- We present a search for associated production of Higgs and W bosons in p (p) over bar collisions at a center of mass energy of root s = 1.96 TeV in 5.3 fb(-1) of integrated luminosity recorded by the DO experiment. Multivariate analysis techniques are applied to events containing one lepton, an imbalance in transverse energy, and one or two b-tagged jets to discriminate a potential WH signal from Standard Model backgrounds. We observe good agreement between data and expected backgrounds, and set an upper limit of 4.5 (at 95% confidence level and for m(H) = 115 GeV) on the ratio of the WH cross section multiplied by the branching fraction of H -> b (b) over bar to its Standard Model prediction, which is consistent with an expected limit of 4.8.
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| 16. |
- Abazov, V. M., et al.
(författare)
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Determination of the pole and (MS)over-bar masses of the top quark from the t(t)over-bar cross section
- 2011
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 703:4, s. 422-427
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Tidskriftsartikel (refereegranskat)abstract
- We use higher-order quantum chromodynamics calculations to extract the mass of the top quark from the t (t) over bar cross section measured in the lepton + jets channel in p (p) over bar collisions at root s = 1.96 TeV using 5.3 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. The extracted top quark pole mass and (MS) over bar mass are compared to the current Tevatron average top quark mass obtained from direct measurements.
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| 17. |
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| 18. |
- Abazov, V. M., et al.
(författare)
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Measurement of Spin Correlation in t(t)over-bar Production Using a Matrix Element Approach
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:3, s. 032001-
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Tidskriftsartikel (refereegranskat)abstract
- We determine the fraction of t (t) over bar events with spin correlation, assuming that the spin of the top quark is either correlated with the spin of the top antiquark as predicted by the standard model or is uncorrelated. For the first time we use a matrix-element-based approach to study t (t) over bar spin correlation. We use t (t) over bar -> W(+)bW(-)(b) over bar -> l(+)nu bl(-)(nu) over bar(b) over bar final states produced in p (p) over bar collisions at a center- of- mass energy root s = 1: 96 TeV, where l denotes an electron or a muon. The data correspond to an integrated luminosity of 5: 4 fb(-1) and were collected with the D0 detector at the Fermilab Tevatron collider. The result agrees with the standard model prediction. We exclude the hypothesis that the spins of the t (t) over bar are uncorrelated at the 97.7% C.L.
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| 19. |
- Abazov, V. M., et al.
(författare)
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Measurement of the t(t)over-bar production cross section using dilepton events in p(p)over-bar collisions
- 2011
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:5, s. 403-410
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the a production cross section sigma((u) over bar) in p (p) over bar collisions at root s = 1.96 TeV using 5.4 fb(-1) of integrated luminosity collected with the D0 detector. We consider final states with at least two jets and two leptons (ee, e mu, mu mu), and events with one jet for the e mu final state as well. The measured cross section is sigma((u) over bar) = 7.36(-0.79)(+0.90)(stat + syst) pb. This result combined with the cross section measurement in the lepton + jets final state yields sigma((u) over bar) = 7.56(-0.56)(+0.63)(stat + syst) pb, which agrees with the standard model expectation. The relative precision of 8% of this measurement is comparable to the precision of the latest theoretical calculations. (C) 2011 Elsevier B.V. All rights reserved.
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| 20. |
- Abazov, V. M., et al.
(författare)
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Measurement of the ZZ production cross section in p(p)over-bar collisions at root s=1.96 TeV
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:1, s. 011103-
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Tidskriftsartikel (refereegranskat)abstract
- We present a new measurement of the production cross section sigma(p (p) over bar -> ZZ) at a center-of-mass energy root s = 1.96 TeV, obtained from the analysis of the four charged lepton final state l(+)l(-)l'(+)l'-(l,l' = e or mu). We observe ten candidate events with an expected background of 0: 37 +/- 0: 13 events. The measured cross section sigma(p (p) over bar -> ZZ) = 1.26(-0.37)(+0.47)(stat) +/- 0.14(syst) pb is in agreement with NLO QCD predictions. This result is combined with a previous result from the ZZ -> l(+)l(-)v (v) over bar channel resulting in a combined cross section of sigma(p (p) over bar -> ZZ) = 1.40(-0.37)(+0.43)(stat) +/- 0.14(syst) pb.
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