| 1. |
- Abazov, V. M., et al.
(författare)
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Measurement of spin correlation in t(t)over-bar production using dilepton final states
- 2011
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 702:1, s. 16-23
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Tidskriftsartikel (refereegranskat)abstract
- We measure the correlation between the spin of the top quark and the spin of the anti-top quark in t (t) over bar -> W(+)bW(-)(b) over bar -> l(+)vbl(-) (v) 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 is an electron or 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 correlation is extracted from the angles of the two leptons in the t and (t) over bar rest frames, yielding a correlation strength C = 0.10(-0.45)(+0.45). in agreement with the NLO QCD prediction within two standard deviations, but also in agreement with the no correlation hypothesis.
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| 2. |
- Abazov, V. M., et al.
(författare)
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Measurement of the WZ -> lvll cross section and limits on anomalous triple gauge couplings 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. ; 695:1-4, s. 67-73
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Tidskriftsartikel (refereegranskat)abstract
- We present a new measurement of the WZ -> lvll (l = e, mu) cross section and limits on anomalous triple gauge couplings. Using 4.1 fb(-1) of integrated luminosity of p (p) over bar collisions at root s = 1.96 TeV, we observe 34 WZ candidate events with an estimated background of 6.0 +/- 0.4 events. We measure the WZ production cross section to be 3.89(-0.90)(+1.07) pb, in good agreement with the standard model prediction. We find no evidence for anomalous WWZ couplings and set 95% C.L. limits on the coupling parameters, -0.077 < lambda(z) < 0.093 and -0.029 < Delta kappa(z) < 0.080 in the HISZ parameterization for a Lambda = 2 TeV form factor scale. These are the best limits to date obtained from the direct measurement of the WWZ vertex.
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| 3. |
- Abazov, V. M., et al.
(författare)
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Measurements of single top quark production cross sections and vertical bar V(tb)vertical bar 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. ; 84:11, s. 112001-
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of production cross sections of single top quarks in p (p) over bar collisions at root s = 1.96 TeV in a data sample corresponding to an integrated luminosity of 5.4 fb(-1) collected by the D0 detector at the Fermilab Tevatron Collider. We select events with an isolated electron or muon, an imbalance in transverse energy, and two, three, or four jets, with one or two of them containing a bottom hadron. We obtain an inclusive cross section of sigma(p (p) over bar -> tb + X, tqb + X) = 3.43(-0.74)(+0.73) pb and use it to extract the CKM matrix element 0.79 < vertical bar V(tb)vertical bar <= 1 at the 95% C.L. We also measure sigma(p<(p)over bar> -> tb + X) = 0.68(-0.35)(+0.38) pb and sigma(p (p) over bar -> tqb + X) = 2.86(-0.63)(+0.69) pb when assuming, respectively, tqb and tb production rates as predicted by the standard model.
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| 4. |
- Abazov, V. M., et al.
(författare)
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W gamma Production and Limits on Anomalous WW gamma Couplings in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:24, s. 241803-
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Tidskriftsartikel (refereegranskat)abstract
- We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(-> l nu) + gamma production in e gamma and mu gamma final states. Using data corresponding to an integrated luminosity of 4.2 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process p (p) over bar -> W gamma + X -> l nu gamma + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WW gamma couplings for data from hadron colliders: -0.4 < Delta kappa(gamma) < 0.4 and -0.08 < lambda(gamma) < 0.07 at the 95% C.L.
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| 5. |
- Abazov, V. M., et al.
(författare)
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Azimuthal decorrelations and multiple parton interactions in gamma+2 jet and gamma+3 jet events in p(p)over-bar collisions at root s=1.96 TeV
- 2011
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Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 83:5, s. 052008-
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Tidskriftsartikel (refereegranskat)abstract
- Samples of inclusive gamma + 2 jet and gamma + 3 jet events collected by the D0 experiment with an integrated luminosity of about 1 fb(-1) in p (p) over bar collisions at root s = 1.96 TeV are used to measure cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (p(T)) of the gamma + leading jet system (jets are ordered in p(T)) and p(T) of the other jet for gamma + 2 jet, or p(T) sum of the two other jets for gamma + 3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo (MC) generators. The data indicate a contribution from events with double parton (DP) interactions and are well-described by predictions provided by the PYTHIA MPI models with p(T)-ordered showers and by SHERPA with the default MPI model. The gamma + 2 jet data are also used to determine the fraction of events with DP interactions as a function of the azimuthal angle and as a function of the second jet p(T).
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| 6. |
- Abazov, V. M., et al.
(författare)
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Bounds on an Anomalous Dijet Resonance in W plus jets Production in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:1, s. 011804-
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the dijet invariant mass spectrum in events with two jets produced in association with a W boson in data corresponding to an integrated luminosity of 4.3 fb(-1) collected with the D0 detector at root s = 1.96 TeV. We find no evidence for anomalous resonant dijet production and derive upper limits on the production cross section of an anomalous dijet resonance recently reported by the CDF Collaboration, investigating the range of dijet invariant mass from 110 to 170 GeV/c(2). The probability of the D0 data being consistent with the presence of a dijet resonance with 4 pb production cross section at 145 GeV/c(2) is 8 x 10(-6).
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| 7. |
- 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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| 8. |
- Abazov, V. M., et al.
(författare)
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Direct measurement of the mass difference between top and antitop quarks
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:5, s. 052005-
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Tidskriftsartikel (refereegranskat)abstract
- We present a direct measurement of the mass difference between top and antitop quarks (Delta m) in lepton + jets t (t) over bar final states using the "matrix element" method. The purity of the lepton + jets sample is enhanced for t (t) over bar events by identifying at least one of the jets as originating from a b quark. The analyzed data correspond to 3.6 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV acquired by D0 in Run II of the Fermilab Tevatron Collider. The combination of the e + jets and mu + jets channels yields Delta m = 0.8 +/- 1.8(stat) +/- 0.5(syst) GeV, which is in agreement with the standard model expectation of no mass difference.
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| 9. |
- Abazov, V. M., et al.
(författare)
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Forward-backward asymmetry in top quark-antiquark production
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:11, s. 112005-
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a data set corresponding to an integrated luminosity of 5.4 fb(-1), collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t (t) over bar forward-backward asymmetry to be (9.2 +/- 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 +/- 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 +/- 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator MC@NLO. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.
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| 10. |
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