| 41. |
- Abazov, V. M., et al.
(författare)
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Measurement of differential tt production cross sections in pp collisions
- 2014
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 90:9, s. 092006-
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Tidskriftsartikel (refereegranskat)abstract
- The production of top quark-antiquark pair events in pp collisions at root s= 1.96 TeV is studied as a function of the transverse momentum and absolute value of the rapidity of the top quarks as well as of the invariant mass of the tt pair. We select events containing an isolated lepton, a large imbalance in transverse momentum, and four or more jets with at least one jet identified as originating from a b quark. The data sample corresponds to 9.7 fb(-1) of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Observed differential cross sections are consistent with standard model predictions.
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| 42. |
- Abazov, V. M., et al.
(författare)
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Measurement of leptonic asymmetries and top-quark polarization in t(t)over-bar production
- 2013
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 87:1, s. 011103-
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of lepton (l) angular distributions in top-quark (t) pair production and t (t) over bar -> W(+)bW-(b) over bar -> l(+) vbl-(v) over bar(b) over bar decays produced in p (p) over bar collisions at a center-of-mass energy of root s = 1.96 TeV, where l is an electron or muon. Using data corresponding to an integrated luminosity of 5.4 fb(-1), collected with the D0 detector at the Fermilab Tevatron Collider, we measure for the first time the leptonic forward-backward asymmetry in dilepton final states and obtain A(FB)(l) = (5.8 +/- 5.1(stat) +/- 1.3(syst))%, corrected for detector acceptance. This is compared to the standard model prediction of A(FB)(l)(predicted) = (4.7 +/- 0.1)%. A deviation from the standard model prediction as previously seen in a D0 measurement based on the analysis of the l + jets final state is not observed in these dilepton final states. The two results differ from each other by 1.4 standard deviations and are combined to obtain A(FB)(l) = (11.8 +/- 3.2)%. Furthermore, we present a first study of the top-quark polarization.
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| 43. |
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| 44. |
- 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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| 45. |
- Abazov, V. M., et al.
(författare)
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Measurement of the asymmetry in angular distributions of leptons produced in dilepton t(t)over-bar final states in p(p)over-bar collisions at root s=1.96 TeV
- 2013
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:11, s. 112002-
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of asymmetries in angular distributions of leptons produced in t (t) over bar events in proton-antiproton collisions at the Fermilab Tevatron Collider. We consider final states where the W-+/- bosons from top quark and antiquark decays both decay into l nu (l = e, mu) resulting in oppositely charged dilepton final states with accompanying jets. Using 9.7 fb(-1) of integrated luminosity collected with the D0 detector, we find the asymmetries in lepton pseudorapidity compatible with predictions based on the standard model.
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| 46. |
- Abazov, V. M., et al.
(författare)
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Measurement of the CP-violating phase phi sJ/psi phi using the flavor-tagged decay Bs(0) -> J/psi phi in 8 fb(-1) of p(p)over-bar collisions
- 2012
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:3, s. 032006-
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Tidskriftsartikel (refereegranskat)abstract
- We report an updated measurement of the CP-violating phase, phi(J/psi phi)(s), and the decay-width difference for the two mass eigenstates, Delta Gamma(s), from the flavor-tagged decay B-s(0) -> J/psi phi. The data sample corresponds to an integrated luminosity of 8.0 fb(-1) accumulated with the D0 detector using p (p) over bar collisions at root s = 1.96 TeV produced at the Fermilab Tevatron collider. The 68% Bayesian credibility intervals, including systematic uncertainties, are Delta Gamma(s) = 0.163(-0.064)(+0.065) ps(-1) and phi(J/psi phi)(s) = -0.55(-0.36)(+0.38). The p-value for the Standard Model point is 29.8%.
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| 47. |
- Abazov, V. M., et al.
(författare)
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Measurement of the CP-violation parameter of B-0 mixing and decay with p(p)over-bar ->mu mu X data
- 2006
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Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 74:9, s. 092001-
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Tidskriftsartikel (refereegranskat)abstract
- We measure the dimuon charge asymmetry A in p (p) over bar collisions at a center of mass energy root s=1960 GeV. The data was recorded with the D0 detector and corresponds to an integrated luminosity of approximately 1.0 fb(-1). Assuming that the asymmetry A is due to asymmetric B-0 <->(B) over bar (0) mixing and decay, we extract the CP-violation parameter of B-0 mixing and decay: ((epsilon B0))/(1+vertical bar epsilon B0 vertical bar 2)=(AB0)/(4)= -0.0023 +/- 0.0011(stat)+/- 0.0008(syst).A(B)(0) is the dimuon charge asymmetry from decays of B-0(B) over bar (0) pairs. The general case, with CP violation in both B-0 and B-s(0) systems, is also considered. Finally we obtain the forward-backward asymmetry that quantifies the tendency of mu(+) to go in the proton direction and mu(-) to go in the antiproton direction. The results are consistent with the standard model and constrain new physics.
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| 48. |
- Abazov, V. M., et al.
(författare)
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Measurement of the differential cross section d sigma/dt in elastic p(p)over-bar scattering at root s=1.96 TeV
- 2012
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:1, s. 012009-
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the elastic differential cross section dσ(pp̅ →pp̅ )/dt as a function of the four-momentum-transfer squared t. The data sample corresponds to an integrated luminosity of ≈31 nb-1 collected with the D0 detector using dedicated Tevatron pp̅ Collider operating conditions at √s=1.96 TeV and covers the range 0.26<|t|<1.2 GeV2. For |t|<0.6 GeV2, dσ/dt is described by an exponential function of the form Ae-b|t| with a slope parameter b=16.86±0.10(stat)±0.20(syst) GeV-2. A change in slope is observed at |t|≈0.6 GeV2, followed by a more gradual |t| dependence with increasing values of |t|.
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| 49. |
- Abazov, V. M., et al.
(författare)
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Measurement of the differential cross section of photon plus jet production in p(p)over-bar collisions at root s=1.96 TeV
- 2013
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:7, s. 072008-
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Tidskriftsartikel (refereegranskat)abstract
- We study the process of associated photon and jet production, p (p) over bar -> gamma + jet + X, using 8.7 fb(-1) of integrated luminosity collected by the D0 detector at the Fermilab Tevatron Collider at a center-of-mass energy root s = 1.96 TeV. Photons are reconstructed with rapidity vertical bar y(gamma)vertical bar < 1.0 or 1.5 < vertical bar y(gamma)vertical bar < 2.5 and transverse momentum p(T)(gamma) > 20 GeV. The highest-p(T) jet is required to be in one of four rapidity regions up to vertical bar y(jet)vertical bar <= 3.2. For each rapidity configuration we measure the differential cross sections in p(T)(gamma) separately for events with the same sign (y(gamma)y(jet) > 0) and opposite signs (y(gamma)y(jet) <= 0) of photon and jet rapidities. We compare the measured triple-differential cross sections, d(3)sigma/dp(T)(gamma)dy(gamma)dy(jet), to next-to-leading order (NLO) perturbative QCD calculations using different sets of parton distribution functions, and to predictions from the SHERPA and PYTHIA Monte Carlo event generators. The NLO calculations are found to be in general agreement with the data but do not describe all kinematic regions.
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| 50. |
- Abazov, V. M., et al.
(författare)
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Measurement of the direct CP-violating parameter A(CP) in the decay D+ -> K-pi(+)pi(+)
- 2014
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 90:11, s. 111102-
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Tidskriftsartikel (refereegranskat)abstract
- We measure the direct CP-violating parameter A(CP) for the decay of the charged charm meson, D+ -> K-pi(+)pi(+)(and charge conjugate), using the full 10.4 fb(-1) sample of p (p) over bar collisions at root s = 1.96 TeV collected by the D0 detector at the Fermilab Tevatron collider. We extract the raw reconstructed charge asymmetry by fitting the invariant mass distributions for the sum and difference of charge-specific samples. This quantity is then corrected for detector-related asymmetries using data-driven methods and for possible physics asymmetries (from B. D processes) using input from Monte Carlo simulation. We measure A(CP) =[-0.16 +/- 0.15(stat) +/- 0.09(syst)] %, which is consistent with zero, as expected from the standard model prediction of CP conservation, and is the most precise measurement of this quantity to date.
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