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1.
  • Schael, S, et al. (författare)
  • Precision electroweak measurements on the Z resonance
  • 2006
  • Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
  • Forskningsöversikt (refereegranskat)abstract
    • We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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2.
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3.
  • Abazov, V. M., et al. (författare)
  • The upgraded DO detector
  • 2006
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 565:2, s. 463-537
  • Tidskriftsartikel (refereegranskat)abstract
    • The DO experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid -argon calorimeters and central muon detector, remaining from Run 1, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DO.
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4.
  • Aaron, F. D., et al. (författare)
  • Multi-leptons with high transverse momentum at HERA
  • 2009
  • Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479. ; :10
  • Tidskriftsartikel (refereegranskat)abstract
    • Events with at least two high transverse momentum leptons (electrons or muons) are studied using the H1 and ZEUS detectors at HERA with an integrated luminosity of 0.94 fb(-1). The observed numbers of events are in general agreement with the Standard Model predictions. Seven di- and tri-lepton events are observed in e(+)p collision data with a scalar sum of the lepton transverse momenta above 100 GeV while 1.94 +/- 0.17 events are expected. Such events are not observed in e(-)p collisions for which 1.19 +/- 0.12 are predicted. Total visible and differential di-electron and di-muon photoproduction cross sections are extracted in a restricted phase space dominated by photon-photon collisions.
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5.
  • Abazov, V. M., et al. (författare)
  • Measurement of the isolated photon cross section in p(p)over-bar collisions at root s=1.96 TeV
  • 2006
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 639:3-4, s. 151-158
  • Tidskriftsartikel (refereegranskat)abstract
    • The cross section for the inclusive production of isolated photons has been measured in p (p) over bar collisions at root s = 1.96 TeV with the DO detector at the Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV and have pseudorapidity vertical bar n vertical bar < 0.9. The cross section is compared with the results from two next-to-leading order perturbative QCD calculations. The theoretical predictions agree with the measurement within uncertainties.
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6.
  • Abazov, V. M., et al. (författare)
  • Search for W ' boson production in the W ' -> t(b)over-bar decay channel
  • 2006
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 641:6, s. 423-431
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a search for the production of a new heavy gauge boson W' that decays to a top quark and a bottom quark. We have analyzed 230 pb(-1) of data collected with the DO detector at the Fermilab Tevatron collider at a center-of-mass energy of 1.96 TeV. No significant excess of events above the standard model expectation is found in any region of the final state invariant mass distribution. We set upper limits on the production cross section of W' bosons times branching ratio to top quarks at the 95% confidence level for several different W, boson masses. We exclude masses between 200 and 610 GeV for a W' boson with standard-model-like couplings, between 200 and 630 GeV for a W, boson with right-handed couplings that is allowed to decay to both leptons and quarks, and between 200 and 670 GeV for a W' boson with right-handed couplings that is only allowed to decay to quarks.
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7.
  • Abazov, V. M., et al. (författare)
  • Evidence for production of single top quarks and first direct measurement of vertical bar V-tb vertical bar
  • 2007
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 98:18, s. 181802-
  • Tidskriftsartikel (refereegranskat)abstract
    • The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron < p(p)over bar > collider. Using a 0.9 fb(-1) dataset, we apply a multivariate analysis to separate signal from background and measure sigma(< p(p)over bar >-> tb+X,tqb+X)=4.9 +/- 1.4 pb. The probability to measure a cross section at this value or higher in the absence of a signal is 0.035%, corresponding to a 3.4 standard deviation significance. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa matrix element that describes the Wtb coupling and find 0.68 <= 1 at 95% C.L. within the standard model.
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8.
  • Abazov, V. M., et al. (författare)
  • Measurement of beta (t -> Wb)/beta(t -> Wq) at root s=1.96 TeV
  • 2006
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 639:6, s. 616-622
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the measurement of R = B(t -> Wb)/B(t -> Wq) in pp collisions at root s = 1.96 TeV, using 230 pb(-1) of data collected by the DO experiment at the Fermilab Tevatron Collider. We fit simultaneously R and the number (N-tt) of selected top quark pairs (tt), to the number of identified b-quark jets in events with one electron or one muon, three or more jets, and high transverse energy imbalance. To improve sensitivity, kinematical properties of events with no identified b-quark jets are included in the fit. We measure R = 1.03(-0.17)(0.19) (stat + syst), in good agreement with the standard model. We set lower limits of R > 0.61 and vertical bar V-tb vertical bar > 0.78 at 95% confidence level.
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9.
  • 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
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 666:5, s. 435-445
  • 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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10.
  • Abazov, V. M., et al. (författare)
  • Measurement of the top quark mass in the dilepton channel
  • 2007
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 655:1-2, s. 7-14
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a measurement of the top quark mass in the dilepton channel based on approximately 370 pb(-1) of data collected by the DO experiment during Run R of the Fermilab Tevatron collider. We employ two different methods to extract the top quark mass. We show that both methods yield consistent results using ensemble tests of events generated with the DO Monte Carlo simulation. We combine the results from the two methods to obtain a top quark mass m(t) = 178.1 +/- 8.2 GeV. The statistical uncertainty is 6.7 GeV and the systematic uncertainty is 4.8 GeV.
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11.
  • Abazov, V. M., et al. (författare)
  • Search for a heavy resonance decaying into a Z plus jet final state in p(p)over-bar collisions at root s=1.96 TeV using the D0 detector
  • 2006
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 74:1, s. 011104-
  • Tidskriftsartikel (refereegranskat)abstract
    • We have searched for a heavy resonance decaying into a Z+jet final state in p (p) over bar collisions at a center of mass energy of 1.96 TeV at the Fermilab Tevatron collider using the D0 detector. No indication for such a resonance was found in a data sample corresponding to an integrated luminosity of 370 pb(-1). We set upper limits on the cross section times branching fraction for heavy resonance production at the 95% C.L. as a function of the resonance mass and width. The limits are interpreted within the framework of a specific model of excited quark production.
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12.
  • Abazov, V. M., et al. (författare)
  • Search for production of single top quarks via tcg and tug flavor-changing-neutral-current couplings
  • 2007
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:19, s. 191802-
  • Tidskriftsartikel (refereegranskat)abstract
    • We search for the production of single top quarks via flavor-changing-neutral-current couplings of a gluon to the top quark and a charm (c) or up (u) quark. We analyze 230 pb(-1) of lepton+jets data from p (p) over tilde collisions at a center of mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We observe no significant deviation from standard model predictions, and hence set upper limits on the anomalous coupling parameters kappa(c)(g)/Lambda and kappa(u)(g)/Lambda, where kappa(g) define the strength of tcg and tug couplings, and Lambda defines the scale of new physics. The limits at 95% C.L. are kappa(c)(g)/Lambda < 0.15 TeV-1 and kappa(u)(g)/Lambda < 0.037 TeV-1.
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13.
  • Abazov, V. M., et al. (författare)
  • Search for R-parity violating supersymmetry via the LL(E)over-bar couplings lambda(121), lambda(122) or lambda(133) in p(p)over-bar collisions at root s=1.96 TeV
  • 2006
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 638:5-6, s. 441-449
  • Tidskriftsartikel (refereegranskat)abstract
    • A search for gaugino pair production with a trilepton signature in the framework of R-parity violating supersymmetry via the couplings; lambda(121), lambda(122), or lambda(133) is presented. The data, corresponding to an integrated luminosity of L approximate to 360 pb(-1), were collected from April 2002 to August 2004 with the D0 detector at the Fermilab Tevatron Collider, at a center-of-mass energy of root s = 1.96 TeV. This analysis considers final states with three charged leptons with the flavor combinations eel, mu mu l, and ee tau (l = e or mu). No evidence for supersymmetry is found and limits at the 95% confidence level are set on the gaugino pair production cross section and lower bounds on the masses of the lightest neutralino and chargino are derived in two supersymmetric models.
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14.
  • Abazov, V. M., et al. (författare)
  • Search for the lightest scalar top quark in events with two leptons in p(p)over-bar collisions at root s=1.96 TeV
  • 2008
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 659:3, s. 500-508
  • Tidskriftsartikel (refereegranskat)abstract
    • Data collected by the DO detector at a p (p) over bar center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider have been used to search for pair production of the lightest supersymmetric partner of the top quark decaying into bl (nu) over tilde. The search is performed in the ll' = e mu and mu mu final states. No evidence for this process has been found in data samples of approximately 400 pb(-1). The domain in the [M((t) over tilde (1)), M((nu) over tilde)] plane excluded at the 95% C.L. is substantially extended by this search.
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15.
  • Abazov, V. M., et al. (författare)
  • A combined search for the standard model Higgs boson at root S=1.96 TeV
  • 2008
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 663:1-2, s. 26-36
  • Tidskriftsartikel (refereegranskat)abstract
    • We present new results of the search for WH --> lvb (b) over bar production in p (p) over bar collisions at a center-of-mass energy of root S = 1.96 TeV, based on a dataset with integrated luminosity of 0.44 fb(-1). We combine these new results with previously published searches by the DO collaboration, for WH and ZH production analyzed in the E(T)b (b) over bar final state, for ZH (--> l(+)l(-)b (b) over bar) production, for WH (-->. WWW) production, and for H (--> W W) direct production. No signal-like excess is observed either in the W H analysis or in the combination of all D0 Higgs boson analyses. We set 95% C.L. (expected) upper limits on sigma(p (p) over bar --> WH) x B(H --> b (b) over bar) ranging from 1.6 (2.2) ph to 1.9 (3.3) pb for Higgs boson masses between 105 and 145 GeV, to be compared to the theoretical prediction of 0.13 pb for a Standard Model (SM) Higgs boson with mass in m(H) = 115 GeV. After combination with the other DO Higgs boson searches, we obtain for in H = 115 GeV an observed (expected) limit 8.5 (12.1) times higher than the SM predicted Higgs boson production cross section. For m(H) = 160 GeV, the corresponding observed (expected) ratio is 10.2 (9.0).
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16.
  • Abazov, V. M., et al. (författare)
  • Determination of the strong coupling constant from the inclusive jet cross section in pp collisions at s=1.96 TeV
  • 2009
  • Ingår i: PHYS REV D. - 1550-7998 .- 1550-2368. ; 80, s. 111107-
  • Tidskriftsartikel (refereegranskat)abstract
    • We determine the strong coupling constant alpha(s) and its energy dependence from the p(T) dependence of the inclusive jet cross section in pp collisions at s=1.96 TeV. The strong coupling constant is determined over the transverse momentum range 50 < p(T)< 145 GeV. Using perturbative QCD calculations to order O(alpha(3)(s)) combined with O(alpha(4)(s)) contributions from threshold corrections, we obtain alpha(s)(M-Z)=0.1161(-0.0048)(+0.0041). This is the most precise result obtained at a hadron-hadron collider.
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17.
  • Abazov, V. M., et al. (författare)
  • Evidence for production of single top quarks
  • 2008
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; D:78, s. 012005-
  • Forskningsöversikt (refereegranskat)abstract
    • We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron p (p) over bar collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top-quark partner that is always produced from strong-coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top-quark production has been searched for in ever larger data sets. In this analysis, we select events from a 0.9 fb(-1) data set that have an electron or muon and missing transverse energy from the decay of a W boson from the top-quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W + jets and t (t) over bar events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix-element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top-quark production of sigma(p (p) over bar -> tb + X, tqb + X) = 4.7 +/- 1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top-quark production. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa quark mixing matrix element that describes the Wtb coupling and find vertical bar V(tb)f(1)(L)vertical bar = 1.31(-0.21)(+0.25), where f(1)(L) is a generic vector coupling. This model-independent measurement translates into 0.68 <= 1 at the 95% C.L. in the standard model.
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18.
  • 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
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:3, s. 032001-:102, s. 032001-
  • 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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19.
  • Abazov, V. M., et al. (författare)
  • Measurement of the B-s(0) lifetime using semileptonic decays
  • 2006
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:24, s. 241801-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a measurement of the B-s(0) lifetime in the semileptonic decay channel B-s(0)-> D-s(-)mu(+)nu X (and its charge conjugate), using approximately 0.4 fb(-1) of data collected with the D0 detector during 2002-2004. Using 5176 reconstructed D-s(-)mu(+) signal events, we have measured the B-s(0) lifetime to be tau(B-s(0))=1.398 +/- 0.044(stat)(-0.025)(+0.028)(syst) ps. This is the most precise measurement of the B-s(0) lifetime to date.
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20.
  • Abazov, V. M., et al. (författare)
  • Measurement of the CP-violation parameter of B-0 mixing and decay with p(p)over-bar ->mu mu X data
  • 2006
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 74:9, s. 092001-
  • 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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21.
  • Abazov, V. M., et al. (författare)
  • Measurement of the Lifetime of the B-c(+/-) Meson in the Semileptonic Decay Channel
  • 2009
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:9, s. 092001-
  • Tidskriftsartikel (refereegranskat)abstract
    • Using approximately 1.3 fb(-1) of data collected by the D0 detector between 2002 and 2006, we measure the lifetime of the B-c(+/-) meson in the B-c(+/-)-> J/psi mu(+/-)+X final state. A simultaneous unbinned likelihood fit to the J/psi+mu invariant mass and lifetime distributions yields a signal of 881 +/- 80(stat) candidates and a lifetime measurement of tau(B-c(+/-))=0.448(-0.036)(+0.038)(stat)+/- 0.032(syst) ps.
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22.
  • Abazov, V. M., et al. (författare)
  • Measurement of the top quark mass in the lepton plus jets final state with the matrix element method
  • 2006
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 74:9, s. 092005-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a measurement of the top quark mass with the matrix element method in the lepton+jets final state. As the energy scale for calorimeter jets represents the dominant source of systematic uncertainty, the matrix element likelihood is extended by an additional parameter, which is defined as a global multiplicative factor applied to the standard energy scale. The top quark mass is obtained from a fit that yields the combined statistical and systematic jet energy scale uncertainty. Using a data set of 0.4 fb(-1) taken with the D0 experiment at Run II of the Fermilab Tevatron Collider, the mass of the top quark is measured using topological information to be: m(top)(center dot+jets)(topo)=169.2(-7.4)(+5.0)(stat+JES)(-1.4)(+1.5)(syst) GeV, and when information about identified b jets is included: m(top)(center dot+jets)(b-tag)=170.3(-4.5)(+4.1)(stat+ JES)(-1.8)(+1.2)(syst) GeV. The measurements yield a jet energy scale consistent with the reference scale.
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23.
  • Abazov, V. M., et al. (författare)
  • Search for a Higgs boson produced in association with a Z boson in p(p)over-bar collisions
  • 2007
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 655:5-6, s. 209-216
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe a search for the Standard Model Higgs boson with a mass of 105 GeV/c(2) to 145 GeV/c(2) in data corresponding to an integrated luminosity of approximately 450 pb(-1) collected with the D phi detector at the Fermilab Tevatron p (p) over bar collider at a center-of-mass energy of 1.96 TeV. The Higgs boson is required to be produced in association with a Z boson, and the Z boson is required to decay to either electrons or muons with the Higgs boson decaying to a b (b) over bar pair. The data are well described by the expected background, leading to 95% confidence level cross section upper limits sigma (p (p) over bar -> ZH) x B(H -> b (b) over bar) in the range of 3.1 pb to 4.4 pb.
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24.
  • Abazov, V. M., et al. (författare)
  • Search for a scalar or vector particle decaying into Z gamma in p(p)over-bar collisions at root s=1.96 TeV
  • 2009
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 671:3, s. 349-355
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a search for a narrow scalar or vector resonance decaying into Z gamma with a subsequent Z boson decay into a pair of electrons or moons. The data for this search were collected with the D circle divide detecror at the Fermilab Tevatron p (p) over bar collider at a center of mass energy root s = 1.96 TeV. Using 1.1 (1.0) fb(-1) of data, we observe 49 (50) candidate events in the electron (muon) channel, in good agreement with the standard model prediction. From the combination of both channels, we derive 95% C.L. upper limits on the cross section times branching fraction (sigma x B) into Z gamma. These limits range from 0.19 (0.20) pb for a scalar (vector) resonance mass of 600 GeV/c(2) to 2.5 (3.1) pb for a mass of 140 GeV/c(2).
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25.
  • Abazov, V. M., et al. (författare)
  • Search for associated Higgs boson production WH -> WWW*-> l(+/-)nu l('+/-)nu(')+X in p(p)over-bar collisions at root S=1.96 TeV
  • 2006
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:15, s. 151804-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a search for associated Higgs boson production in the process p (p) over bar -> WH -> WWW*-> l(+/-)nu l('+/-)nu(')+X in final states containing two like-sign isolated electrons or muons (e(+/-)e(+/-), e(+/-)mu(+/-), or mu(+/-)mu(+/-)). The search is based on D0 run II data samples corresponding to integrated luminosities of 360-380 pb(-1). No excess is observed over the predicted standard model background. We set 95% C.L. upper limits on sigma ->(p (p) over bar WH) x Br(H -> WW*) between 3.2 and 2.8 pb for Higgs boson masses from 115 to 175 GeV.
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26.
  • Abazov, V. M., et al. (författare)
  • Search for Higgs bosons decaying to tau pairs in p(p)over-bar collisions with the D0 detector
  • 2008
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 101:7, s. 071804-:101, s. 071804-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a search for the production of neutral Higgs bosons phi decaying into tau(+)tau(-) final states in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of approximately 1 fb(-1), were collected by the D0 experiment at the Fermilab Tevatron Collider. Limits on the production cross section times branching ratio are set. The results are interpreted in the minimal supersymmetric standard model yielding limits that are the most stringent to date at hadron colliders.
  •  
27.
  • Abazov, V. M., et al. (författare)
  • Search for neutral Higgs bosons decaying to tau pairs in p(p)over-bar collisions at root s=1.96 TeV
  • 2006
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:12, s. 121802-
  • Tidskriftsartikel (refereegranskat)abstract
    • A search for the production of neutral Higgs bosons Phi decaying into tau(+)tau(-) final states in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV is presented. The data, corresponding to an integrated luminosity of approximately 325 pb(-1), were collected by the D0 experiment at the Fermilab Tevatron Collider. Since no excess compared to the expectation from standard model processes is found, limits on the production cross section times branching ratio are set. The results are combined with those obtained from the D0 search for Phi b((b) over bar)-> b (b) over barb((b) over bar) and are interpreted in the minimal supersymmetric standard model.
  •  
28.
  • Abazov, V. M., et al. (författare)
  • Search for pair production of second generation scalar leptoquarks
  • 2009
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 671:2, s. 224-232
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a search for the pair production of second generation scalar leptoquarks (LQ) in p (p) over bar collisions at the center of mass energy root s- = 1.96 TeV using a data set corresponding to an integrated luminosity of 1.0 fb(-1) collected with the D empty set experiment at the Fermilab Tevatron Collider. Topologies arising from the LQ (LQ) over bar -> mu q nu q and LQ (LQ) over bar -> mu q mu q decay modes are investigated. No excess of data over the standard model prediction is observed and upper limits on the leptoquark pair production cross section are derived at the 95% C.L. as a function of the leptoquark mass and the branching fraction beta for the decay LQ -> mu q. These are interpreted as lower limits on the leptoquark mass as a function of beta. For beta = 1 (0.5), scalar second generation leptoquarks with masses up to 316 GeV (270 GeV) are excluded.
  •  
29.
  • Abazov, V. M., et al. (författare)
  • Search for particles decaying into a Z boson and a photon in p(p)over-bar collisions at root s=1.96 TeV
  • 2006
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 641:6, s. 415-422
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the results of a search for a new particle X produced in p (p) over bar collisions at root s- = 1.96 TeV and subsequently decaying to Z gamma. The search uses 0.3 fb(-1) of data collected with the DO detector at the Fermilab Tevatron Collider. We set limits on the production cross section times the branching fraction sigma(p (p) over bar -> X) x B(X -> Z gamma) that range from 0.4 to 3.5 pb at the 95% C.L. for X with invariant masses between 100 and 1000 GeV/c(2), over a wide range of X decay widths.
  •  
30.
  • Abazov, V. M., et al. (författare)
  • Search for resonant second generation slepton production at the Fermilab Tevatron
  • 2006
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:11, s. 111801-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a search for supersymmetry in the R-parity violating resonant production and decay of smuons and muon sneutrinos in the channels mu ->chi(0)(1)mu, mu ->chi(0)(2,3,4)mu, and nu(mu)->chi(+/-)(1,2)mu. We analyzed 0.38 fb(-1) of integrated luminosity collected between April 2002 and August 2004 with the D0 detector at the Fermilab Tevatron Collider. The observed number of events is in agreement with the standard model expectation, and we calculate 95% C.L. limits on the slepton production cross section times branching fraction to gaugino plus muon, as a function of slepton and gaugino masses. In the framework of minimal supergravity, we set limits on the coupling parameter lambda(')(211), extending significantly previous results obtained in Run I of the Tevatron and at the CERN LEP collider.
  •  
31.
  •  
32.
  • Abazov, V. M., et al. (författare)
  • Search for supersymmetry in di-photon final states at root s=1.96 TeV
  • 2008
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 659:5, s. 856-863
  • Tidskriftsartikel (refereegranskat)abstract
    • We report results of a search for supersymmetry (SUSY) with gauge-mediated symmetry breaking in di-photon events collected by the DO experiment at the Fermilab Tevatron Collider in 2002-2006. In 1.1 fb(-1) of data, we find no significant excess beyond the background expected from the standard model and set the most stringent lower limits to date for a standard benchmark model on the lightest neutralino and chargino masses of 125 GeV and 229 GeV, respectively, at 95% confidence.
  •  
33.
  • Abazov, V. M., et al. (författare)
  • Search for the rare decay B-s(0)->phi mu(+)mu(-) with the D0 detector
  • 2006
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 74:3, s. 031107-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a search for the flavor-changing neutral current decay B-s(0)->phi mu(+)mu(-) using about 0.45 fb(-1) of data collected in p (p) over bar collisions at root s=1.96 TeV with the D0 detector at the Fermilab Tevatron Collider. We find an upper limit on the branching ratio of this decay normalized to B-s(0)-> J/psi phi of B(B-s(0)->phi mu(+)mu(-))/B(B-s(0)-> J/psi phi)< 4.4x10(-3) at the 95% C.L. Using the central value of the world average branching fraction of B-s(0)-> J/psi phi, the limit corresponds to B(B-s(0)->phi mu(+)mu(-))< 4.1x10(-6) at the 95% C.L., the most stringent upper bound to date.
  •  
34.
  • Abazov, V. M., et al. (författare)
  • Search for the standard model Higgs boson in the p(p)over-bar -> ZH -> v(v)over-barb(b)over-bar channel
  • 2006
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:16, s. 161803-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a search for the standard model (SM) Higgs boson based on data collected by the D0 experiment at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 260 pb(-1). We study events with missing transverse energy and two acoplanar b jets, which provide sensitivity to the ZH production cross section in the nu nu bb channel, and to WH production when the lepton from the W ->center dot nu decay is undetected. The data are consistent with the SM background expectation, and we set 95% C.L. upper limits on sigma(pp -> ZH/WH) x B(H -> bb) from 3.4/8.3 to 2.5/6.3 pb, for Higgs-boson masses between 105 and 135 GeV.
  •  
35.
  • Abazov, V. M., et al. (författare)
  • Search for W ' boson resonances decaying to a top quark and a bottom quark
  • 2008
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:21, s. 211803-:100, s. 211803-
  • Tidskriftsartikel (refereegranskat)abstract
    • We search for the production of a heavy W ' gauge boson that decays to third generation quarks in 0: 9 fb(-1) of p (p) over bar collisions at root s = 1: 96 TeV, collected with the D0 detector at the Fermilab Tevatron collider. We find no significant excess in the final-state invariant mass distribution and set upper limits on the production cross section times branching fraction. For a left-handed W ' boson with SM couplings, we set a lower mass limit of 731 GeV. For right-handed W ' bosons, we set lower mass limits of 739 GeV if the W ' boson decays to both leptons and quarks and 768 GeV if the W ' boson decays only to quarks. We also set limits on the coupling of the W ' boson to fermions as a function of its mass.
  •  
36.
  • Abazov, V. M., et al. (författare)
  • Combined D0 measurements constraining the CP-violating phase and width difference in the B-s(0) system
  • 2007
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 76:5, s. 057101-
  • Tidskriftsartikel (refereegranskat)abstract
    • We combine the D0 measurement of the width difference between the light and heavy B-s(0) mass eigenstates and of the CP-violating mixing phase determined from the time-dependent angular distributions in the B-s(0)-> J/psi phi decays along with the charge asymmetry in semileptonic decays also measured with the D0 detector. With the additional constraint from the world average of the flavor-specific B-s(0) lifetime, we obtain Delta Gamma(s)equivalent to(Gamma(L)-Gamma(H))=0.13 +/- 0.09 ps(-1) and vertical bar phi(s)vertical bar=0.70(-0.47)(+0.39) or Delta Gamma(s)=-0.13 +/- 0.09 ps(-1) and vertical bar phi(s)vertical bar=2.44(-0.39)(+0.47). The data sample corresponds to an integrated luminosity of 1.1 fb(-1) accumulated with the D0 detector at the Fermilab Tevatron Collider.
  •  
37.
  • Abazov, V. M., et al. (författare)
  • Direct observation of the strange b baryon Xi(-)(b)
  • 2007
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:5, s. 052001-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the first direct observation of the strange b baryon Xi(-)(b)(Xi) over bar (+)(b)). We reconstruct the decay Xi(-)(b)-->J/psi Xi(-), with J/psi-->mu(+)mu(-), and Xi(-)-->Lambda pi(-)-->p pi(-)pi(-) in p (p) over bar collisions at root s = 1.96 TeV. Using 1.3 fb(-1) of data collected by the D0 detector, we observe 15.2 +/- 4.4(stat)(-0.4)(+1.9)(syst) Xi(-)(b) candidates at a mass of 5.774 +/- 0.011(stat) +/- 0.015(syst) GeV. The significance of the observed signal is 5.5 sigma, equivalent to a probability of 3.3 x 10(-8) of it arising from a background fluctuation. Normalizing to the decay Lambda(b)-->J/psi Lambda, we measure the relative rate sigma(Xi(-)(b))xB(Xi(-)(b)-->J/psi Xi)/ sigma(Lambda(b))xB(Lambda(b)-->J/psi Lambda) = 0.28 +/- 0.09(stat)(-0.08)(+0.09)(syst).
  •  
38.
  • Abazov, V. M., et al. (författare)
  • Evidence for the Decay B-s(0)->(DsDs(*))-D-(*) and a Measurement of Delta Gamma(CP)(s)/Gamma(s)
  • 2009
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:9, s. 091801-
  • Tidskriftsartikel (refereegranskat)abstract
    • We search for the semi-inclusive process B-s(0)->(DsDs(*))-D-(*) using 2.8 fb(-1) of pp collisions at s=1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We observe 26.6 +/- 8.4 signal events with a significance above background of 3.2 standard deviations yielding a branching ratio of B(B-s(0)->(DsDs(*))-D-(*))=0.035 +/- 0.010(stat.)+/- 0.011(syst.). Under certain theoretical assumptions, these double-charm final states saturate CP-even eigenstates in the B-s(0) decays resulting in a width difference of Delta Gamma(CP)(s)/Gamma(s)=0.072 +/- 0.021(stat.)+/- 0.022(syst.).
  •  
39.
  • Abazov, V. M., et al. (författare)
  • Experimental discrimination between charge 2e/3 top quark and charge 4e/3 exotic quark production scenarios
  • 2007
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 98:4, s. 041801-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first experimental discrimination between the 2e/3 and 4e/3 top quark electric charge scenarios, using top quark pairs (t (t) over bar) produced in p (p) over bar collisions at root s =1.96 TeV by the Fermilab Tevatron Collider. We use 370 pb(-1) of data collected by the D0 experiment and select events with at least one high transverse momentum electron or muon, high transverse energy imbalance, and four or more jets. We discriminate between b- and (b) over bar -quark jets by using the charge and momenta of tracks within the jet cones. The data are consistent with the expected electric charge, |q|=2e/3. We exclude, at the 92% C.L., that the sample is solely due to the production of exotic quark pairs Q (Q) over bar with |q|=4e/3. We place an upper limit on the fraction of Q (Q) over bar pairs rho < 0.80 at the 90% C.L.
  •  
40.
  • 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-
  • 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.
  •  
41.
  • Abazov, V. M., et al. (författare)
  • Limits on anomalous trilinear gauge couplings from WW -> e(+)e(-), WW -> e(+/-)mu(-/+), and WW ->mu(+)mu(-) events from pp collisions at root s=1.96 TeV
  • 2006
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 74:5, s. 057101-
  • Tidskriftsartikel (refereegranskat)abstract
    • Limits are set on anomalous WW gamma and WWZ trilinear gauge couplings using W+W--> e(+)nu(e)e(-)(nu) over bar (e), W+W--> e(+/-)nu(e)mu(-/+)nu(mu), and W+W-->mu(+)nu(mu)mu(-)(nu) over bar (mu) events. The data set was collected by the Run II D0 detector at the Fermilab Tevatron Collider and corresponds to approximately 250 pb(-1) of integrated luminosity at root s=1.96 TeV. Under the assumption that the WW gamma couplings are equal to the WWZ couplings and using a form factor scale of Lambda=2.0 TeV, the combined 95% C.L. one-dimensional coupling limits from all three channels are -0.32
  •  
42.
  • Abazov, V. M., et al. (författare)
  • Measurement of B-d mixing using opposite-side flavor tagging
  • 2006
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 74:11, s. 112002-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a measurement of the B-d(0) mixing frequency and the calibration of an opposite-side flavor tagger in the D0 experiment. Various properties associated with the b quark on the opposite side of the reconstructed B meson are combined using a likelihood-ratio method into a single variable with enhanced tagging power. Its performance is tested with data, using a large sample of reconstructed semileptonic B ->mu(DX)-X-0 and B ->mu(DX)-X-* decays, corresponding to an integrated luminosity of approximately 1 fb(-1). The events are divided into groups depending on the value of the combined tagging variable, and an independent analysis is performed in each group. Combining the results of these analyses, the overall effective tagging power is found to be epsilon D-2=(2.48 +/- 0.21(-0.06)(+0.08))%. The measured B-d(0) mixing frequency Delta m(d)=0.506 +/- 0.020(stat)+/- 0.016(syst) ps(-1) is in good agreement with the world average value.
  •  
43.
  • Abazov, V. M., et al. (författare)
  • Measurement of sigma(p(p)over-bar -> Z plus X)Br(Z -> tau(+)tau(-)) at root s=1.96 TeV
  • 2009
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 670:4-5, s. 292-299
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a measurement of the cross section for Z boson production times the branching fraction to tau lepton pairs sigma(p (p) over bar -> Z + X)Br(Z -> tau(+)tau(-)) in p (p) over bar collisions at root s = 1.96 TeV. The measurement is performed in the channel in which one tau lepton decays into a muon and neutrinos. and the other tau lepton decays hadronically or into an electron and neutrinos. The data sample corresponds to an integrated luminosity of 1.0 fb(-1) collected with the DO detector at the Fermilab Tevatron Collider. The sample contains 1511 candidate events with an estimated 20% background from jets or muons misidentified as tau leptons. We obtain sigma . Br = 240 +/- 8 (star) +/- 12 (sys) +/- 15 (lum) pb, which is consistent with the standard model prediction.
  •  
44.
  • Abazov, V. M., et al. (författare)
  • Measurement of the forward-backward charge asymmetry in top-quark pair production
  • 2008
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:14:100, s. 142002-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first measurement of the integrated forward-backward charge asymmetry in top-quark-top-antiquark pair (t (t) over bar) production in proton-antiproton (p (p) over bar) collisions in the lepton+jets final state. Using a b-jet tagging algorithm and kinematic reconstruction assuming t (t) over bar +X production and decay, a sample of 0.9 fb(-1) of data, collected by the D0 experiment at the Fermilab Tevatron Collider, is used to measure the asymmetry for different jet multiplicities. The result is also used to set upper limits on t (t) over bar +X production via a Z' resonance.
  •  
45.
  • Abazov, V. M., et al. (författare)
  • Measurement of the Lambda(0)(b) lifetime using semileptonic decays
  • 2007
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:18, s. 182001-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a measurement of the Lambda(0)(b) lifetime using a sample corresponding to 1.3 fb(-1) of data collected by the D0 experiment in 2002-2006 during run II of the Fermilab Tevatron collider. The Lambda(0)(b) baryon is reconstructed via the decay Lambda(0)(b)->mu(nu) over bar Lambda X-+(c). Using 4437 +/- 329 signal candidates, we measure the Lambda(0)(b) lifetime to be tau(Lambda(0)(b))=1.290(-0.110)(+0.119)(stat)(-0.091)(+0.087)(syst) ps, which is among the most precise measurements in semileptonic Lambda(0)(b) decays. This result is in good agreement with the world average value.
  •  
46.
  • Abazov, V. M., et al. (författare)
  • Measurement of the muon charge asymmetry from W boson decays
  • 2008
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; D:77, s. 011106-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a measurement of the muon charge asymmetry from W boson decays using 0.3 fb(-1) of data collected at root s =1.96 GeV between 2002 and 2004 with the D0 detector at the Fermilab Tevatron (p) over bar Collider. We compare our findings with expectations from next-to-leading-order calculations performed using the CTEQ6.1M and MRST04 NLO parton distribution functions. Our findings can be used to constrain future parton distribution function fits.
  •  
47.
  • Abazov, V. M., et al. (författare)
  • Measurement of the p(p)over-bar -> t(t)over-bar + X production cross section at root s=1.96 TeV in the fully hadronic decay channel
  • 2007
  • Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 76:7, s. 072007-
  • Tidskriftsartikel (refereegranskat)abstract
    • A measurement of the top quark pair production cross section in proton antiproton collisions at an interaction energy of root s=1.96 TeV is presented. This analysis uses 405 +/- 25 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron Collider. Fully hadronic t (t) over bar decays with final states of six or more jets are separated from the multijet background using secondary vertex tagging and a neural network. The t (t) over bar cross section is measured as sigma(t (t) over bar)=4.5(-1.9)(+2.0)(stat)(-1.1)(+1.4)(syst)+/- 0.3(lumi) pb for a top quark mass of m(t)=175 GeV/c(2).
  •  
48.
  • Abazov, V. M., et al. (författare)
  • Measurement of the p(p)over-bar -> WZ+X cross section at root s=1.96 TeV and limits on WWZ trilinear gauge couplings
  • 2007
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 76:11
  • Tidskriftsartikel (refereegranskat)abstract
    • We present measurements of the process p (P) over bar -> WZ + X -> l 'nu(l ')l (l) over bar at root s = 1:96 TeV,where l and l ' are electrons or muons. Using 1 fb(-1) of data from the D0 experiment, we observe 13 candidates with an expected background of 4.5 +/- 0.6 events and measure a cross section sigma(WZ) = 2.7(-1.3)(+1.7) pb. From the number of observed events and the Z boson transverse momentum distribution, we limit the trilinear WWZ gauge couplings to -0: 17 <= lambda(Z) <= 0.21 (Delta k(Z) <= 0.29(lambda(Z) = 0) at the 95% C.L. for a form factor scale Lambda = 2 TeV. Further, assuming that Delta g(1)(Z) = Delta k(Z), we find -0.12 <= Delta k(Z) <= 0.29(lambda(Z) = 0) at the 95% C. L. These are the most restrictive limits on the WWZ couplings available to date.
  •  
49.
  • Abazov, V. M., et al. (författare)
  • Measurement of the ratios of the Z/gamma*+ >= n jet production cross sections to the total inclusive Z/gamma* cross section in p(p)over-bar collisions at root s=1.96 TeV
  • 2008
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 658, s. 112-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a study of events with Z bosons and associated jets produced at the Fermilab Tevatron collider in p p collisions at a center of mass energy of 1.96 TeV The data sample consists of nearly 14000 Z/gamma* -> e(+)e(-) candidates corresponding to an integrated luminosity of 0.4 fb(-1) collected with the D circle divide detector. Ratios of the Z/gamma*+ >= n jet cross sections to the total inclusive Z/gamma* cross section have been measured for n = 1-4 jets, and found to be in good agreement with a next-to-leading order QCD calculation and with a tree-level QCD prediction with parton shower simulation and hadronization.
  •  
50.
  • Abazov, V. M., et al. (författare)
  • Measurement of the Semileptonic Branching Ratio of Bs(0) to an Orbitally Excited D-s** State : Br(Bs(0) -> Ds1(-)(2536)mu(+)nu X)
  • 2009
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:5, s. 051801-:102, s. 051801-
  • Tidskriftsartikel (refereegranskat)abstract
    • In a data sample of approximately 1.3 fb(-1) collected with the D0 detector between 2002 and 2006, the orbitally excited charm state D-s1(+/-)(2536) has been observed with a measured mass of 2535.7 +/- 0.6(stat) +/- 0.5(syst) MeV/c(2) via the decay mode B-s(0) -> D-s1(-)(2536)mu(+)nu X-mu. A first measurement is made of the branching ratio product Br((b) over bar -> D-s1(-)(2536)mu(+)nu X-mu) x Br(D-s1(-) -> D*K--(S)0). Assuming that D-s1(-)(2536) production in semileptonic decay is entirely from B-s(0), an extraction of the semileptonic branching ratio Br(B-s(0) -> D-s1(-)(2536)mu(+)nu X-mu) is made.
  •  
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