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1.
  • Aaltonen, T., et al. (author)
  • Combination of Tevatron Searches for the Standard Model Higgs Boson in the W+W- Decay Mode
  • 2010
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:6, s. 061802-
  • Journal article (peer-reviewed)abstract
    • We combine searches by the CDF and D0 Collaborations for a Higgs boson decaying to W+W-. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb(-1) of p (p) over bar collisions at root s = 1.96 TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard model Higgs boson in the mass range 162-166 GeV at the 95% C.L.
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2.
  • Aaltonen, T., et al. (author)
  • Evidence for a Particle Produced in Association with Weak Bosons and Decaying to a Bottom-Antibottom Quark Pair in Higgs Boson Searches at the Tevatron
  • 2012
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:7, s. 071804-
  • Journal article (peer-reviewed)abstract
    • We combine searches by the CDF and D0 Collaborations for the associated production of a Higgs boson with a W or Z boson and subsequent decay of the Higgs boson to a bottom-antibottom quark pair. The data, originating from Fermilab Tevatron p (p) over bar collisions at root s = 1.96 TeV, correspond to integrated luminosities of up to 9.7 fb(-1). The searches are conducted for a Higgs boson with mass in the range 100-150 GeV/c(2). We observe an excess of events in the data compared with the background predictions, which is most significant in the mass range between 120 and 135 GeV/c(2). The largest local significance is 3.3 standard deviations, corresponding to a global significance of 3.1 standard deviations. We interpret this as evidence for the presence of a new particle consistent with the standard model Higgs boson, which is produced in association with a weak vector boson and decays to a bottom-antibottom quark pair.
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3.
  • Aaltonen, T., et al. (author)
  • Combination of CDF and D0 measurements of the W boson helicity in top quark decays
  • 2012
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:7, s. 071106-
  • Journal article (peer-reviewed)abstract
    • We report the combination of recent measurements of the helicity of the W boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of 2.7-5.4 fb(-1) of p (p) over bar collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of W bosons with longitudinal (f(0)) and right-handed (f(+)) helicities, we find f(0) = 0.722 +/- 0.081[+/- 0.062(stat) +/- 0.052(syst)] and f(+) = -0.033 +/- 0.046[+/- 0.034(stat) +/- 0.031(syst)]. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find f(0) = 0.682 +/- 0.057[+/- 0.035(stat) +/- 0.046(syst)] for fixed f(+) and f(+) = -0.015 +/- 0.035[+/- 0.018(stat) +/- 0.030(syst)] for fixed f(0). The results are consistent with standard model expectations.
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4.
  • Abazov, V. M., et al. (author)
  • Dependence of the t(t)over-bar production cross section on the transverse momentum of the top quark
  • 2010
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 693:5, s. 515-521
  • Journal article (peer-reviewed)abstract
    • We present a measurement of the differential cross section for t (t) over bar events produced in p (p) over bar collisions at root s = 1.96 TeV as a function of the transverse momentum (p(T)) of the top quark. The selected events contain a high-p(T) lepton (l), a large imbalance in p(T). four or more jets with at least one candidate for a b jet, and correspond to 1 fb(-1) of integrated luminosity recorded with the D0 detector. Objects in the event are associated through a constrained kinematic fit to the t (t) over bar -> WbW (b) over bar -> lvbq (q) over bar' (b) over bar process. Results from next and next-to-next-to-leading-order perturbative QCD calculations agree with the measured differential cross section. Comparisons are also provided to predictions from Monte Carlo event generators using QCD calculations at different levels of precision. (C) 2010 Elsevier B.V. All rights reserved.
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5.
  • Abazov, V. M., et al. (author)
  • Search for single top quarks in the tau plus jets channel using 4.8 fb(-1) of p(p)over-bar collision data
  • 2010
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 690:1, s. 5-14
  • Journal article (peer-reviewed)abstract
    • We present the first direct search for single top quark production using reconstructed tau leptons in the final state. The search is based on 4.8 fb(-1) of integrated luminosity collected in p (p) over bar collisions at root s= 1.96 TeV with the D0 detector at the Fermilab Tevatron Collider. We select events with a final state including an isolated tau lepton. missing transverse energy, two or three jets, one or two of them being identified as b quark jet. We use a multivariate technique to discriminate signal from background. The number of events observed in data in this final state is consistent with the signal plus background expectation. We set in the tau + jets channel an upper limit on the single top quark cross section of 7.3 pb at the 95% C.L. This measurement allows a gain of 4% in expected sensitivity for the observation of single top production when combining it with electron + jets and muon + jets channels already published by the DO Collaboration with 2.3 fb(-1) of data. We measure a combined cross section of 3.84(-0.83)(+0.89) pb, which is the most precise measurement to date.
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6.
  • Abazov, V. M., et al. (author)
  • Search for the Standard Model Higgs Boson in the ZH -> v(v)over-barb(b)over-bar Channel in 5.2 fb(-1) of p(p)over-bar Collisions at root s=1.96 TeV
  • 2010
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:7, s. 071801-
  • Journal article (peer-reviewed)abstract
    • A search is performed for the standard model Higgs boson in 5.2 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV, collected with the D0 detector at the Fermilab Tevatron Collider. The final state considered is a pair of b jets and large missing transverse energy, as expected from p (p) over bar -> ZH -> v (v) over barb (b) over bar production. The search is also sensitive to the WH -> lvb (b) over bar channel when the charged lepton is not identified. For a Higgs boson mass of 115 GeV, a limit is set at the 95% C.L. on the cross section multiplied by branching fraction for [p (p) over bar -> (Z/W)H](H -> b (b) over bar) that is a factor of 3.7 larger than the standard model value, consistent with the factor of 4.6 expected.
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7.
  • Abazov, V. M., et al. (author)
  • Determination of the strong coupling constant from the inclusive jet cross section in pp collisions at s=1.96 TeV
  • 2009
  • In: PHYS REV D. - 1550-7998 .- 1550-2368. ; 80, s. 111107-
  • Journal article (peer-reviewed)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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8.
  • Abazov, V. M., et al. (author)
  • Double parton interactions in gamma+3 jet events in p(p)over-bar collisions at root s=1.96 TeV
  • 2010
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 81:5, s. 052012-
  • Journal article (peer-reviewed)abstract
    • 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 <= p(T)(jet2) <= 30 GeV. In this range, f(DP) varies between 0.23 <= f(DP) <= 0.47, while sigma(eff) has the average value sigma(ave)(eff) = 16.4 +/- 0.3(stat) +/- 2.3(syst) mb.
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9.
  • Abazov, V. M., et al. (author)
  • Measurement of the t(t)over-bar cross section using high-multiplicity jet events
  • 2010
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 82, s. 032002-
  • Journal article (peer-reviewed)abstract
    • We present a measurement of the t (t) over bar cross section using high-multiplicity jet events produced in p (p) over bar collisions at root s = 1.96 TeV. These data were recorded at the Fermilab Tevatron Collider with the D0 detector. Events with at least six jets, two of them identified as b jets, were selected from a 1 fb(-1) data set. The measured cross section, assuming a top quark mass of 175 GeV/c(2), is 6.9 +/- 2.0 pb, in agreement with theoretical expectations.
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10.
  • Abazov, V. M., et al. (author)
  • Search for a Resonance Decaying into WZ Boson Pairs in p(p)over-bar Collisions
  • 2010
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:6, s. 061801-
  • Journal article (peer-reviewed)abstract
    • We present the first search for an electrically charged resonance W' decaying to a WZ boson pair using 4.1 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron p (p) over bar collider. The WZ pairs are reconstructed through their decays into three charged leptons (l = e, mu). A total of 9 data events is observed in good agreement with the background prediction. We set 95% C.L. limits on the W'WZ coupling and on the W' production cross section multiplied by the branching fractions. We also exclude W' masses between 188 and 520 GeV within a simple extension of the standard model and set the most restrictive limits to date on low-scale technicolor models.
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11.
  • Abazov, V. M., et al. (author)
  • Search for Higgs Boson Production in Dilepton and Missing Energy Final States with 5.4 fb(-1) of p(p)over-bar Collisions at root s=1.96 TeV
  • 2010
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:6, s. 061804-
  • Journal article (peer-reviewed)abstract
    • A search for the standard model Higgs boson is presented using events with two charged leptons and large missing transverse energy selected from 5.4 fb(-1) of integrated luminosity in p ($) over bar collisions at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron collider. No significant excess of events above background predictions is found, and observed (expected) upper limits at 95% confidence level on the rate of Higgs boson production are derived that are a factor of 1.55 (1.36) above the predicted standard model cross section at m(H) = 165 GeV.
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12.
  • Abazov, V. M., et al. (author)
  • Search for the Associated Production of a b Quark and a Neutral Supersymmetric Higgs Boson that Decays into τ Pairs
  • 2010
  • In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 104:15
  • Journal article (peer-reviewed)abstract
    • We report results from a search for production of a neutral Higgs boson in association with a b quark. We search for Higgs decays to tau pairs with one tau subsequently decaying to a muon and the other to hadrons. The data correspond to 2: 7 fb(-1) of p (p) over bar collisions recorded by the D0 detector at.. root s = 1.96 TeV. The data are found to be consistent with background predictions. The result allows us to exclude a significant region of parameter space of the minimal supersymmetric model.
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13.
  • Abazov, V. M., et al. (author)
  • Measurement of the dijet invariant mass cross section in p(p)over-bar collisions at root s=1.96 TeV
  • 2010
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 693:5, s. 531-538
  • Journal article (peer-reviewed)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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14.
  • Abazov, V. M., et al. (author)
  • b-Jet identification in the D0 experiment
  • 2010
  • In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 620:2-3, s. 490-517
  • Journal article (peer-reviewed)abstract
    • 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.
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15.
  • Abazov, V. M., et al. (author)
  • Evidence for an anomalous like-sign dimuon charge asymmetry
  • 2010
  • In: Physical Review D. - 1550-7998. ; 82:13, s. 032001-
  • Journal article (peer-reviewed)abstract
    • 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.
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16.
  • Abazov, V. M., et al. (author)
  • Evidence for an Anomalous Like-Sign Dimuon Charge Asymmetry
  • 2010
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 105:8, s. 081801-
  • Journal article (peer-reviewed)abstract
    • 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.
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17.
  • Abazov, V. M., et al. (author)
  • Measurement of direct photon pair production cross sections in p(p)over-bar collisions at root s=1.96 TeV
  • 2010
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 690:2, s. 108-117
  • Journal article (peer-reviewed)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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18.
  • Abazov, V. M., et al. (author)
  • Measurement of the inclusive jet cross section in p(p)over-bar collisions at root s=1.96 TeV
  • 2012
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:5
  • Journal article (peer-reviewed)abstract
    • We present a measurement of the inclusive jet cross section using the Run II cone algorithm and data collected by the D0 experiment in p (p) over bar collisions at a center-of-mass energy root s = 1.96 TeV, corresponding to an integrated luminosity of 0: 70 fb(-1). The jet energy calibration and the method used to extract the inclusive jet cross section are described. We discuss the main uncertainties, which are dominated by the jet energy scale uncertainty. The results cover jet transverse momenta from 50 GeV to 600 GeV with jet rapidities in the range -2.4 to 2.4 and are compared to predictions using recent proton parton distribution functions. Studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented.
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19.
  • Abazov, V. M., et al. (author)
  • Measurement of the normalized Z/gamma* -> mu(+)mu(-) transverse momentum distribution in p(p)over-bar collisions at root s=1.96 TeV
  • 2010
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 693:5, s. 522-530
  • Journal article (peer-reviewed)abstract
    • 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* -> 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.
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20.
  • Abazov, V. M., et al. (author)
  • Measurement of the WZ -> lvll cross section and limits on anomalous triple gauge couplings in p(p)over-bar collisions at root s=1.96 TeV
  • 2011
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 695:1-4, s. 67-73
  • Journal article (peer-reviewed)abstract
    • We present a new measurement of the WZ -> 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 < lambda(z) < 0.093 and -0.029 < Delta kappa(z) < 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.
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21.
  • Abazov, V. M., et al. (author)
  • 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
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:11, s. 112001-
  • Journal article (peer-reviewed)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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22.
  • Abazov, V. M., et al. (author)
  • Model-independent measurement of t-channel single top quark production in p(p)over-bar collisions at,root s=1.96 TeV
  • 2011
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 705:4, s. 313-319
  • Journal article (peer-reviewed)abstract
    • We present a model-independent measurement of t-channel electroweak production of single top quarks in p collisions at root s = 1.96 TeV. Using 5.4 fb(-1) of integrated luminosity collected by the DO detector at the Fermilab Tevatron Collider, and selecting events containing an isolated electron or muon, missing transverse energy and one or two jets originating from the fragmentation of b quarks, we measure a cross section sigma (p (p) over bar -> tqb + X) = 2.90 +/- 0.59 (stat + syst) pb for a top quark mass of 172.5 GeV. The probability of the background to fluctuate and produce a signal as large as the one observed is 1.6 x 10(-8), corresponding to a significance of 5.5 standard deviations. (C) 2011 Elsevier B.V. All rights reserved.
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23.
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24.
  • Abazov, V. M., et al. (author)
  • Search for scalar bottom quarks and third-generation leptoquarks in p(p)over-bar collisions at root s=1.96 TeV
  • 2010
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 693:2, s. 95-101
  • Journal article (peer-reviewed)abstract
    • We report the results of a search for pair production of scalar bottom quarks ((b) over bar (1)) and scalar third-generation leptoquarks (LQ(3)) in 5.2 fb(-1) of p (p) over bar collisions at the D0 experiment of the Fermilab Tevatron Collider. Scalar bottom quarks are assumed to decay to a neutralino ((chi) over bar (1)(0)) and a b quark, and we set 95% C.L. lower limits on their production in the (m((b) over bar1), m((chi) over bar 10)) mass plane such as m((b) over bar1) > 247 GeV for m(<(chi)over) (bar>10) = 0 and m((chi) over bar 10) > 110 GeV for 160 m(<(b) over bar1) < 200 GeV. The leptoquarks are assumed to decay to a tau neutrino and a b quark, and we set a 95% C.L. lower limit of 247 GeV on the mass of a charge-1/3 third-generation scalar leptoquark.
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25.
  • Abazov, V. M., et al. (author)
  • Search for the rare decay B-s(0) -> mu(+)mu(-)
  • 2010
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 693:5, s. 539-544
  • Journal article (peer-reviewed)abstract
    • We present the results of a search for the flavor changing neutral current decay B-s(0) -> 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) -> mu(+)mu(-)) < 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.
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26.
  • Abazov, V. M., et al. (author)
  • Bounds on an Anomalous Dijet Resonance in W plus jets Production in p(p)over-bar Collisions at root s=1.96 TeV
  • 2011
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:1, s. 011804-
  • Journal article (peer-reviewed)abstract
    • We present a study of the dijet invariant mass spectrum in events with two jets produced in association with a W boson in data corresponding to an integrated luminosity of 4.3 fb(-1) collected with the D0 detector at root s = 1.96 TeV. We find no evidence for anomalous resonant dijet production and derive upper limits on the production cross section of an anomalous dijet resonance recently reported by the CDF Collaboration, investigating the range of dijet invariant mass from 110 to 170 GeV/c(2). The probability of the D0 data being consistent with the presence of a dijet resonance with 4 pb production cross section at 145 GeV/c(2) is 8 x 10(-6).
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27.
  • Abazov, V. M., et al. (author)
  • Determination of the pole and (MS)over-bar masses of the top quark from the t(t)over-bar cross section
  • 2011
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 703:4, s. 422-427
  • Journal article (peer-reviewed)abstract
    • We use higher-order quantum chromodynamics calculations to extract the mass of the top quark from the t (t) over bar cross section measured in the lepton + jets channel in p (p) over bar collisions at root s = 1.96 TeV using 5.3 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. The extracted top quark pole mass and (MS) over bar mass are compared to the current Tevatron average top quark mass obtained from direct measurements.
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28.
  • Abazov, V. M., et al. (author)
  • Determination of the Width of the Top Quark
  • 2011
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:2, s. 022001-
  • Journal article (peer-reviewed)abstract
    • We extract the total width of the top quark, Gamma(t), from the partial decay width Gamma(t -> Wb) measured using the t-channel cross section for single top-quark production and from the branching fraction B(t -> Wb) measured in t (t) over bar t events using up to 2.3 fb(-1) of integrated luminosity collected by the D0 Collaboration at the Tevatron p (p) over bar Collider. The result is Gamma(t) = 1.99(-0.55)(+0.69) GeV, which translates to a top-quark lifetime of tau(t) = (3.3-(+1.3)(0.9)) x 10(-25) s. Assuming a high mass fourth generation b' quark and unitarity of the four-generation quark-mixing matrix, we set the first upper limit on vertical bar V-tb'vertical bar < 0.63 at 95% C.L.
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29.
  • Abazov, V. M., et al. (author)
  • Direct measurement of the mass difference between top and antitop quarks
  • 2011
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:5, s. 052005-
  • Journal article (peer-reviewed)abstract
    • We present a direct measurement of the mass difference between top and antitop quarks (Delta m) in lepton + jets t (t) over bar final states using the "matrix element" method. The purity of the lepton + jets sample is enhanced for t (t) over bar events by identifying at least one of the jets as originating from a b quark. The analyzed data correspond to 3.6 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV acquired by D0 in Run II of the Fermilab Tevatron Collider. The combination of the e + jets and mu + jets channels yields Delta m = 0.8 +/- 1.8(stat) +/- 0.5(syst) GeV, which is in agreement with the standard model expectation of no mass difference.
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30.
  • Abazov, V. M., et al. (author)
  • Forward-backward asymmetry in top quark-antiquark production
  • 2011
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:11, s. 112005-
  • Journal article (peer-reviewed)abstract
    • We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a data set corresponding to an integrated luminosity of 5.4 fb(-1), collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t (t) over bar forward-backward asymmetry to be (9.2 +/- 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 +/- 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 +/- 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator MC@NLO. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.
  •  
31.
  • Abazov, V. M., et al. (author)
  • High mass exclusive diffractive dijet production in p(p)over-bar collisions at root s=1.96 TeV
  • 2011
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 705:3, s. 193-199
  • Journal article (peer-reviewed)abstract
    • We present evidence for diffractive exclusive dijet production with an invariant dijet mass greater than 100 GeV in data collected with the DO experiment at the Fermilab Tevatron Collider. A discriminant based on calorimeter information is used to measure a significant number of events with little energy (typically less than 10 GeV) outside the dijet system, consistent with the diffractive exclusive dijet production topology. The probability for these events to be explained by other dijet production processes is 2 x 10(-6), corresponding to a 4.7 standard deviation significance.
  •  
32.
  • Abazov, V. M., et al. (author)
  • Improved determination of the width of the top quark
  • 2012
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:9, s. 091104-
  • Journal article (peer-reviewed)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.
  •  
33.
  •  
34.
  • Abazov, V. M., et al. (author)
  • Measurement of Spin Correlation in t(t)over-bar Production Using a Matrix Element Approach
  • 2011
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:3, s. 032001-
  • Journal article (peer-reviewed)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.
  •  
35.
  • Abazov, V. M., et al. (author)
  • Measurement of t(t)over-bar production in the tau plus jets topology using p(p)over-bar collisions root s=1.96 TeV
  • 2010
  • In: PHYS REV D. - 1550-7998. ; 82:7, s. 071102-
  • Journal article (peer-reviewed)abstract
    • We present a measurement of the t (t) over bar production cross section multiplied by the branching ratio to tau lepton decaying semihadronically (tau(h)) plus jets, sigma(p (p) over bar -> t (t) over bar + X) center dot BR(t (t) over bar -> tau(h) + jets), at a center of mass energy root s = 1.96 TeV using 1 fb(-1) of integrated luminosity collected with the D0 detector. Assuming a top quark mass of 170 GeV, we measure sigma(t (t) over bar) center dot BR tau h (+ j) = 0.60(-0.22)(+0.23)(stat)(-0.14)(+0.15)(syst) +/- 0.04(lumi) pb. In addition, we extract the t (t) over bar production cross section using the t (t) over bar -> tau(h) + jets topology, with the result sigma(t (t) over bar) = 6.9(-1.2)(+1.2)(stat)(-0.7)(+0.8)(syst) +/- 0.4(lumi) pb. These findings are in good agreement with standard model predictions and measurements performed using other top quark decay channels.
  •  
36.
  • Abazov, V. M., et al. (author)
  • Measurement of the anomalous like-sign dimuon charge asymmetry with 9 fb(-1) of p(p)over-bar collisions
  • 2011
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:5, s. 052007-
  • Journal article (peer-reviewed)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.
  •  
37.
  • Abazov, V. M., et al. (author)
  • 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
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:3, s. 032006-
  • Journal article (peer-reviewed)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%.
  •  
38.
  • Abazov, V. M., et al. (author)
  • Measurement of the differential cross section d sigma/dt in elastic p(p)over-bar scattering at root s=1.96 TeV
  • 2012
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:1, s. 012009-
  • Journal article (peer-reviewed)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|.
  •  
39.
  • Abazov, V. M., et al. (author)
  • Measurement of the t(t)over-bar production cross section using dilepton events in p(p)over-bar collisions
  • 2011
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:5, s. 403-410
  • Journal article (peer-reviewed)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.
  •  
40.
  • Abazov, V. M., et al. (author)
  • Measurement of the ZZ production cross section in p(p)over-bar collisions at root s=1.96 TeV
  • 2011
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:1, s. 011103-
  • Journal article (peer-reviewed)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.
  •  
41.
  • Abazov, V. M., et al. (author)
  • 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
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:5, s. 434-441
  • Journal article (peer-reviewed)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.
  •  
42.
  • Abazov, V. M., et al. (author)
  • 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
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 705:3, s. 200-207
  • Journal article (peer-reviewed)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.
  •  
43.
  • Abazov, V. M., et al. (author)
  • Model indedpendent search for new phenomena in p(p)over-bar collisions at root s=1.96 TeV
  • 2012
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:9, s. 092015-
  • Journal article (peer-reviewed)abstract
    • We describe a model-independent search for physics beyond the standard model in lepton final states. We examine 117 final states using 1.1 fb(-1) of p (p) over bar collisions data at root s = 1.96 TeV collected with the D0 detector. We conclude that all observed discrepancies between data and model can be attributed to uncertainties in the standard model background modeling, and hence we do not see any evidence for physics beyond the standard model.
  •  
44.
  • Abazov, V. M., et al. (author)
  • Precise measurement of the top-quark mass from lepton plus jets events at D0
  • 2011
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:3, s. 032004-
  • Journal article (peer-reviewed)abstract
    • We report a measurement of the mass of the top quark in lepton + jets final states of p (p) over bar -> t (t) over bar data corresponding to 2.6 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. A matrix-element method is developed that combines an in situ jet energy calibration with our standard jet energy scale derived from studies of gamma + jet and dijet events. We then implement a flavor-dependent jet-response correction through a novel approach. This method is used to measure a top-quark mass of m(t) = 176.01 +/- 1.64 GeV. Combining this result with our previous result obtained on an independent data set, we measure a top-quark mass of m(t) = 174.94 +/- 1.49 GeV for a total integrated luminosity of 3.6 fb(-1).
  •  
45.
  • Abazov, V. M., et al. (author)
  • Precise Measurement of the Top Quark Mass in the Dilepton Channel at D0
  • 2011
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:8, s. 082004-
  • Journal article (peer-reviewed)abstract
    • We measure the top quark mass (m(t)) in p (p) over bar collisions at a center of mass energy root s = 1.96 TeV using dilepton t (t) over bar -> W(+)bW(-)b(-) -> l(+)nu(l)bl(-)(nu) over bar (l)(b) over bar events, where l denotes an electron, a muon, or a tau that decays leptonically. The data correspond to an integrated luminosity of 5.4 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider. We obtain m(t) = 174.0 +/- 1.8(stat) +/- 2.4(syst) GeV, which is in agreement with the current world average m(t) = 173.3 +/- 1.1 GeV. This is currently the most precise measurement of mt in the dilepton channel.
  •  
46.
  • Abazov, V. M., et al. (author)
  • Precise Study of the Z/gamma* Boson Transverse Momentum Distribution in p(p)over-bar Collisions Using a Novel Technique
  • 2011
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:12, s. 122001-
  • Journal article (peer-reviewed)abstract
    • Using 7.3 fb(-1) of p (p) over bar collisions collected by the D0 detector at the Fermilab Tevatron, we measure the distribution of the variable phi(eta)*, which probes the same physical effects as the Z/gamma* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. A QCD prediction is found to describe the general features of the phi(eta)* distribution, but is unable to describe its detailed shape or dependence on boson rapidity. A prediction that includes a broadening of transverse momentum for small values of the parton momentum fraction is strongly disfavored.
  •  
47.
  • Abazov, V. M., et al. (author)
  • Precision Measurement of the Ratio B(t -> Wb)/B(t -> Wq) and Extraction of V(tb)
  • 2011
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:12, s. 121802-
  • Journal article (peer-reviewed)abstract
    • We present a measurement of the ratio of top quark branching fractions R = B(t -> Wb)/B(t -> Wq), where q can be a d, s, or b quark, in the lepton + jets and dilepton t (t) over bar final states. The measurement uses data from 5: 4 fb(-1) of p (p) over bar collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure R = 0.90 +/- 0.04, and we extract the Cabibbo-Kobayashi-Maskawa (CKM) matrix element vertical bar V(tb)vertical bar as vertical bar V(tb)vertical bar = 0.95 +/- 0.02, assuming unitarity of the 3 x 3 CKM matrix.
  •  
48.
  • Abazov, V. M., et al. (author)
  • Search for a Fermiophobic and Standard Model Higgs Boson in Diphoton Final States
  • 2011
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:15, s. 151801-
  • Journal article (peer-reviewed)abstract
    • We present a search for the standard model Higgs boson and a fermiophobic Higgs boson in the diphoton final states based on 8.2 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No excess of data above background predictions is observed and upper limits at the 95% C.L. on the cross section multiplied by the branching fraction are set which are the most restrictive to date. A fermiophobic Higgs boson with a mass below 112.9 GeV is excluded at the 95% C.L.
  •  
49.
  • Abazov, V. M., et al. (author)
  • Search for a Fourth Generation t ' Quark in p(p)over-bar Collisions at root s=1.96 TeV
  • 2011
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:8, s. 082001-
  • Journal article (peer-reviewed)abstract
    • We present a search for pair production of a fourth generation t' quark and its antiparticle, followed by their decays to a W boson and a jet, based on an integrated luminosity of 5: 3 fb(-1) of proton-antiproton collisions at root s = 1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the t'(t) over bar' production cross section that exclude at the 95% C. L. a t' quark that decays exclusively to W + jet with a mass below 285 GeV. We observe a small excess in the mu + jets channel which reduces the mass range excluded compared to the expected limit of 320 GeV in the absence of a signal.
  •  
50.
  • Abazov, V. M., et al. (author)
  • Search for a heavy neutral gauge boson in the dielectron channel with 5.4 fb(-1) of p(p)over-bar collisions at root s=1.96 TeV
  • 2011
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 695:1-4, s. 88-94
  • Journal article (peer-reviewed)abstract
    • We report the results of a search for a heavy neutral gauge boson Z' decaying into the dielectron final state using data corresponding to an integrated luminosity of 5.4 fb(-1) collected by the D0 experiment at the Fermilab Tevatron Collider. No significant excess above the standard model prediction is observed in the dielectron invariant-mass spectrum. We set 95 sigma(p (p) over bar -> Z') x BR(Z' -> ee) depending on the dielectron invariant mass. These cross section limits are used to determine lower mass limits for bosons in a variety of models. For the sequential standard model boson a lower mass limit of 1023 GeV is obtained.
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