| 41. |
- Abazov, V. M., et al.
(författare)
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Improved determination of the width of the top quark
- 2012
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:9, s. 091104-
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Tidskriftsartikel (refereegranskat)abstract
- We present an improved determination of the total width of the top quark, Gamma(t), using 5.4 fb(-1) of integrated luminosity collected by the D0 Collaboration at the Tevatron p (p) over bar Collider. The total width Gamma(t) is extracted from the partial decay width Gamma(t -> Wb) and the branching fraction B(t -> Wb). Gamma(t -> Wb) is obtained from the t-channel single top-quark production cross section and B(t -> Wb) is measured in t (t) over bar events. For a top mass of 172.5 GeV, the resulting width is Gamma(t) = 2.00(-0.43)(+0.47) GeV. This translates to a top-quark lifetime of tau(t) = (3.29(-0.63)(+0.90)) x 10(-25) s. We also extract an improved direct limit on the Cabibbo-Kobayashi-Maskawa quark-mixing matrix element 0.81 < vertical bar V-tb vertical bar <= 1 at 95% C.L. and a limit of vertical bar V-tb'vertical bar < 0.59 for a high-mass fourth-generation bottom quark assuming unitarity of the fourth-generation quark-mixing matrix.
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| 42. |
- Abazov, V. M., et al.
(författare)
-
Lifetime difference and CP-violating phase in the B-s(0) system
- 2007
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 98:12, s. 121801-
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Tidskriftsartikel (refereegranskat)abstract
- From an analysis of the decay B-s(0)-> J/psi phi, we obtain the width difference between the light and heavy mass eigenstates Delta Gamma equivalent to(Gamma(L)-Gamma(H))=0.17 +/- 0.09(stat)+/- 0.02(syst) ps(-1) and the CP-violating phase phi(s)=-0.79 +/- 0.56(stat)(-0.01)(+0.14)(syst). Under the hypothesis of no CP violation (phi(s)equivalent to 0), we obtain 1/Gamma=tau/(B-s(0))=1.52 +/- 0.08(stat)(-0.03)(+0.01)(syst) ps and Delta Gamma=0.12(-0.10)(+0.08)(stat)+/- 0.02(syst) ps(-1). The data sample corresponds to an integrated luminosity of about 1.1 fb(-1) accumulated with the D0 detector at the Fermilab Tevatron collider. This is the first direct measurement of the CP-violating mixing phase in the B-s(0) system.
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| 43. |
- Abazov, V. M., et al.
(författare)
-
Measurement of direct photon pair production cross sections in p(p)over-bar collisions at root s=1.96 TeV
- 2010
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 690:2, s. 108-117
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of direct photon pair production cross sections using 4.2 fb(-1) of data collected with the DO detector at the Fermilab Tevatron p (p) over bar Collider. We measure single differential cross sections as a function of the diphoton mass, the transverse momentum of the diphoton system, the azimuthal angle between the photons, and the polar scattering angle of the photons. In addition, we measure double differential cross sections considering the last three kinematic variables in three diphoton mass bins. The results are compared with different perturbative QCD predictions and event generators. (C) 2010 Elsevier B.V. All rights reserved.
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| 44. |
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| 45. |
- Abazov, V. M., et al.
(författare)
-
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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| 46. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the Angular and Lifetime Parameters of the Decays B-d(0) -> J/psi K*(0) and B-s(0) -> J/psi phi
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:3, s. 032001-:102, s. 032001-
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of the linear polarization amplitudes and the strong relative phases that describe the flavor-untagged decays B-d(0) --> J/psi K*(0) and B-s(0) --> J/psi phi in the transversity basis. We also measure the mean lifetime (tau) over bar (s) of the B-s(0) mass eigenstates and the lifetime ratio (tau) over bar (s)/tau(d). The analyses are based on approximately 2.8 fb(-1) of data recorded with the D0 detector. From our measurements of the angular parameters we conclude that there is no evidence for a deviation from flavor SU( 3) symmetry for these decays and that the factorization assumption is not valid for the B-d(0) --> J/psi K*(0) decay.
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| 47. |
- Abazov, V. M., et al.
(författare)
-
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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| 48. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the charge asymmetry in semileptonic B-s(0) decays
- 2007
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 98:15, s. 151801-
-
Tidskriftsartikel (refereegranskat)abstract
- We have performed the first direct measurement of the time-integrated flavor untagged charge asymmetry in semileptonic B-s(0) decays A(SL)(s,unt) by comparing the decay rate of B-s(0) -> mu(+) D-s(-) nu X, where D-s(-) -> phi pi(-) and phi -> K+K-, with the charge-conjugate (B) over bar (0)(s) decay rate. This sample was selected from 1: 3 fb(-1) of data collected by the D0 experiment in run II of the Fermilab Tevatron collider. We obtain A(SL)(s,unt) = [1.23 +/- 0.97(stat) +/- 0.17(syst)] x 10(-2). Assuming that Delta m(s)/(Gamma) over bar (s) >> 1, this result can be translated into a measurement of the CP-violating phase in B-s(0) mixing: Delta Gamma(s)/Delta m(s) tan phi(s) = [2.45 +/- 1.93(stat) +/- 0.35(syst)] x 10(-2).
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| 49. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the differential cross section for the production of an isolated photon with associated jet in p(p)over-bar collisions at root s=1.96 TeV
- 2008
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 666:5, s. 435-445
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Tidskriftsartikel (refereegranskat)abstract
- The process p (p) over bar -> gamma + jet + X is studied using 1.0 fb(-1) of data collected by the DO detector at the Fermilab Tevatron p (p) over bar collider at a center-of-mass energy root s = 1.96 TeV. Photons are reconstructed in the central rapidity region vertical bar y(gamma)vertical bar < 1.0 with transverse momenta in the range 30 < p(T)(gamma) < 400 GeV while jets are reconstructed in either the central vertical bar y(jet)vertical bar < 0.8 or forward 1.5 < vertical bar y(jet)vertical bar < 2.5 rapidity intervals with P-T(jet) > 15 GeV. The differential cross section d(3 sigma)/dp(T)(gamma) dy(gamma) dy(jet) is measured as a function of p(T)(gamma) in four regions, differing by the relative orientations of the photon and the jet in rapidity. Ratios between the differential cross sections in each region are also presented. Next-to-leading order QCD predictions using different parameterizations of parton distribution functions and theoretical scale choices are compared to the data. The predictions do not simultaneously describe the measured normalization and p(T)(gamma) dependence of the cross section in the four measured regions.
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| 50. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the dijet invariant mass cross section in p(p)over-bar collisions at root s=1.96 TeV
- 2010
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 693:5, s. 531-538
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Tidskriftsartikel (refereegranskat)abstract
- The inclusive dijet production double differential cross section as a function of the dijet invariant mass and of the largest absolute rapidity of the two jets with the largest transverse momentum in an event is measured in p (p) over bar collisions at root s = 1.96 TeV using 0.7 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The measurement is performed in six rapidity regions up to a maximum rapidity of 2.4. Next-to-leading order perturbative QCD predictions are found to be in agreement with the data. (C) 2010 Elsevier B.V. All rights reserved.
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