| 241. |
- Abazov, V. M., et al.
(författare)
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Measurement of the anomalous like-sign dimuon charge asymmetry with 9 fb(-1) of p(p)over-bar collisions
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:5, s. 052007-
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Tidskriftsartikel (refereegranskat)abstract
- We present an updated measurement of the anomalous like-sign dimuon charge asymmetry A(sl)(b) for semileptonic b-hadron decays in 9.0 fb(-1) of p (p) over bar collisions recorded with the D0 detector at a center-of-mass energy of root s = 1.96 TeV at the Fermilab Tevatron collider. We obtain A(sl)(b) = (-0.787 +/- 0.172(stat) +/- 0.093(syst)%. This result differs by 3.9 standard deviations from the prediction of the standard model and provides evidence for anomalously large CP violation in semileptonic neutral B decay. The dependence of the asymmetry on the muon impact parameter is consistent with the hypothesis that it originates from semileptonic b-hadron decays.
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| 242. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the production fraction times branching fraction f(b -> Lambda(b)) . B(Lambda(b) -> J/psi Lambda)
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:3, s. 031102-
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Tidskriftsartikel (refereegranskat)abstract
- The Lambda(b)(udb) baryon is observed in the decay Lambda(b) -> J/psi Lambda using 6.1fb(-1) of p (p) over bar collisions collected with the D0 detector at root s = 1/96 TeV. The production fraction multiplied by the branching fraction for this decay relative to that for the decay B(0) -> J/psi K(s)(0) is measured to be 0.345 +/- 0.034(stat) +/- 0.033(syst) +/- 0.003(PDG). Using the world average value of f(b -> B(0)) . B(B(0) -> J/psi K(s)(0) = (1.74 +/- 0.08) x 10(-5), we obtain f(b -> Lambda(b)) . B(Lambda(b) -> J/psi Lambda) = (6.01 +/- 0.60(stat) +/- 0.58(syst) +/- 0.28(PDG)) x 10(-5). This measurement represents an improvement in precision by about a factor of 3 with respect to the current world average.
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| 243. |
- Abazov, V. M., et al.
(författare)
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Measurement of the ratio of inclusive cross sections sigma(p(p)over-bar -> Z plus b-quark jet)/sigma(p(p)over-bar -> Z plus jet) at root s=1.96 TeV
- 2011
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Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 83:3, s. 031105-
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Tidskriftsartikel (refereegranskat)abstract
- The ratio of the cross section for p (p) over bar interactions producing a Z boson and at least one b-quark jet to the inclusive Z + jet cross section is measured using 4.2 fb(-1) of p (p) over bar collisions collected with the D0 detector at the Fermilab Tevatron collider at root s = 1.96 TeV. The Z -> l(+) l- candidate events with at least one b jet are discriminated from Z + charm and light jet(s) events by a novel technique that exploits the properties of the tracks associated to the jet. The measured ratio is 0: 0193 +/- 0: 0027 for events having a jet with transverse momentum p(T) > 20 GeV and pseudorapidity vertical bar eta vertical bar <= 2.5, which is the most precise to date and is consistent with theoretical predictions.
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| 244. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the t(t)over-bar production cross section using dilepton events in p(p)over-bar collisions
- 2011
-
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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| 245. |
- 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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| 246. |
- 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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| 247. |
- Abazov, V. M., et al.
(författare)
-
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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| 248. |
- Abazov, V. M., et al.
(författare)
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Measurement of three-jet differential cross sections d sigma(3jet)/dM(3jet) in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:5, s. 434-441
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Tidskriftsartikel (refereegranskat)abstract
- We present the first measurement of the inclusive three-jet differential cross section as a function of the invariant mass of the three jets with the largest transverse momenta in an event in p (p) over bar collisions at root s = 1.96 TeV. The measurement is made in different rapidity regions and for different jet transverse momentum requirements and is based on a data set corresponding to an integrated luminosity of 0.7 fb(-1) collected with the DO detector at the Fermilab Tevatron Collider. The results are used to test the three-jet matrix elements in perturbative QCD calculations at next-to-leading order in the strong coupling constant. The data allow discrimination between parametrizations of the parton distribution functions of the proton. (C) 2011 Elsevier B.V. All rights reserved.
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| 249. |
- Abazov, V. M., et al.
(författare)
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Measurements of inclusive W plus jets production rates as a function of jet transverse momentum in p(p)over-bar collisions root s=1.96 TeV
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 705:3, s. 200-207
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Tidskriftsartikel (refereegranskat)abstract
- This Letter describes measurements of inclusive W (-> ev) + n jet cross sections (n = 1-4), presented as total inclusive cross sections and differentially in the nth jet transverse momentum. The measurements are made using data corresponding to an integrated luminosity of 4.2 fb(-1) collected by the DO detector at the Fermilab Tevatron Collider, and achieve considerably smaller uncertainties on W + jets production cross sections than previous measurements. The measurements are compared to next-to-leading order perturbative QCD (pQCD) calculations in the n = 1-3 jet multiplicity bins and to leading order pQCD calculations in the 4-jet bin. The measurements are generally in agreement with pQCD calculations, although certain regions of phase space are identified where these predictions could better match the data.
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| 250. |
- 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
-
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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