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1.
  • Abazov, V. M., et al. (författare)
  • b-Jet identification in the D0 experiment
  • 2010
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. - 0168-9002 .- 1872-9576. ; 620:2-3, s. 490-517
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Algorithms distinguishing jets originating from b quarks from other jet flavors are important tools in the physics program of the D0 experiment at the Fermilab Tevatron p (p) over bar collider. This article describes the methods that have been used to identify b-quark jets, exploiting in particular the long lifetimes of b-flavored hadrons, and the calibration of the performance of these algorithms based on collider data.</p>
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2.
  • 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
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 690:2, s. 108-117
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>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.</p>
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3.
  • 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
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 693:5, s. 531-538
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>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.</p>
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4.
  • Abazov, V. M., et al. (författare)
  • Measurement of the normalized Z/gamma* -&gt; mu(+)mu(-) transverse momentum distribution in p(p)over-bar collisions at root s=1.96 TeV
  • 2010
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 693:5, s. 522-530
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present a new measurement of the Z/gamma* transverse momentum distribution in the range 0-330 GeV, in proton-antiproton collisions at root s = 1.96 TeV. The measurement uses 0.97 fb(-1) of integrated luminosity recorded by the D0 experiment and is the first using the Z/gamma* -&gt; mu(+)mu(-) + X channel at this center-of-mass energy. This is also the first measurement of the Z/gamma* transverse momentum distribution that presents the result at the level of particles entering the detector, minimizing dependence on theoretical models. As any momentum of the Z/gamma* in the plane transverse to the incoming beams must be balanced by some recoiling system, primarily the result of QCD radiation in the initial state, this variable is an excellent probe of the underlying process. Tests of the predictions of QCD calculations and current event generators show they have varied success in describing the data. Using this measurement as an input to theoretical predictions will allow for a better description of hadron collider data and hence it will increase experimental sensitivity to rare signals. (C) 2010 Elsevier B.V. All rights reserved.</p>
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5.
  • Abazov, V. M., et al. (författare)
  • Measurement of the WZ -&gt; lvll cross section and limits on anomalous triple gauge couplings in p(p)over-bar collisions at root s=1.96 TeV
  • 2011
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 695:1-4, s. 67-73
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present a new measurement of the WZ -&gt; 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 &lt; lambda(z) &lt; 0.093 and -0.029 &lt; Delta kappa(z) &lt; 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.</p>
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6.
  • Abazov, V. M., et al. (författare)
  • Search for flavor changing neutral currents via quark-gluon couplings in single top quark production using 2.3 fb(-1) of p(p)over-bar collisions
  • 2010
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 693:2, s. 81-87
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present a search for flavor changing neutral currents via quark-gluon couplings in a sample of single top quark final states corresponding to 2.3 fb(-1) of integrated luminosity collected with the DO detector at the Fermilab Tevatron Collider. We select events containing a single top quark candidates with an additional jet, and obtain separation between signal and background using Bayesian neural networks. We find consistency between background expectation and observed data, and set limits on flavor changing neutral current gluon couplings of the top quark to up quarks (tgu) and charm quarks (tgc). The cross section limits at the 95% C.L. are sigma(tgu) &lt; 0.20 pb and sigma(tgc) &lt; 0.27 pb. These correspond to limits on the top quark decay branching fractions of B(t -&gt; gu) &lt; 2.0 x 10(-4) and B(t -&gt; gc) &lt; 3.9 x 10(-3).</p>
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7.
  • Abazov, V. M., et al. (författare)
  • Search for the rare decay B-s(0) -&gt; mu(+)mu(-)
  • 2010
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 693:5, s. 539-544
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We present the results of a search for the flavor changing neutral current decay B-s(0) -&gt; mu(+)mu(-) using 6.1 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron Collider. The observed number of B-s(0) candidates is consistent with background expectations. The resulting upper limit on the branching fraction is B(B-s(0) -&gt; mu(+)mu(-)) &lt; 5.1 x 10(-8) at the 95% C.L. This limit is a factor of 2.4 better than that of the previous DO analysis and the best limit to date. Published by Elsevier B.V.</p>
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8.
  • Abazov, V. M., et al. (författare)
  • Double parton interactions in gamma+3 jet events in p(p)over-bar collisions at root s=1.96 TeV
  • 2010
  • Ingår i: Physical Review D. - 1550-7998. ; 81:5, s. 052012
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We have used a sample of gamma + 3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb(-1) to determine the fraction of events with double parton scattering (f(DP)) in a single p (p) over bar collision at root s = 1.96 TeV. The DP fraction and effective cross section (sigma(eff)), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p(T)) jet transverse momentum p(T)(jet2) within the range 15 &lt;= p(T)(jet2) &lt;= 30 GeV. In this range, f(DP) varies between 0.23 &lt;= f(DP) &lt;= 0.47, while sigma(eff) has the average value sigma(ave)(eff) = 16.4 +/- 0.3(stat) +/- 2.3(syst) mb.</p>
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9.
  • Abazov, V. M., et al. (författare)
  • Evidence for an Anomalous Like-Sign Dimuon Charge Asymmetry
  • 2010
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 105:8, s. 081801
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We measure the charge asymmetry A =(N++ -N--)/(N++ + N--) of like-sign dimuon events in 6.1 fb(-1) of p (p) over bar collisions recorded with the D0 detector at a center-of-mass energy root s = 1: 96 TeV at the Fermilab Tevatron collider. From A we extract the like-sign dimuon charge asymmetry in semileptonic b-hadron decays: A(sl)(b) = -0.009 57 +/- 0.00251(stat) +/- 0.001 46(sys). It differs by 3.2 standard deviations from the standard model prediction A(sl)(b)(SM) = (-2.3(-0.6)(+0.5)) x 10(-4), and provides first evidence of anomalous CP violation in the mixing of neutral B mesons.</p>
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10.
  • Abazov, V. M., et al. (författare)
  • Evidence for an anomalous like-sign dimuon charge asymmetry
  • 2010
  • Ingår i: Physical Review D. - 1550-7998. ; 82:3, s. 032001
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>We measure the charge asymmetry A of like-sign dimuon events in 6.1 fb(-1) of p (p) over bar collisions recorded with the D0 detector at a center-of-mass energy root s = 1.96 TeV at the Fermilab Tevatron collider. From A, we extract the like-sign dimuon charge asymmetry in semileptonic b-hadron decays: A(sl)(b) = -0.00957 +/- 0.00251 (stat) +/- 0.00146 (syst). This result differs by 3.2 standard deviations from the standard model prediction A(sl)(b)(SM) = (-2.3(0.6)(+0.5)) x 10(-4) and provides first evidence of anomalous CP violation in the mixing of neutral B mesons.</p>
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