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Search: WFRF:(Ross L.) > (2010-2014)

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1.
  • Acharya, B. S., et al. (author)
  • Introducing the CTA concept
  • 2013
  • In: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 43, s. 3-18
  • Journal article (other academic/artistic)abstract
    • The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. (C) 2013 Elsevier B.V. All rights reserved.
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2.
  • 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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3.
  • 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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4.
  • Aaltonen, T., et al. (author)
  • Combination of CDF and D0 W-Boson mass measurements
  • 2013
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052018-
  • Journal article (peer-reviewed)abstract
    • We summarize and combine direct measurements of the mass of the W boson in root s = 1.96 TeV proton-antiproton collision data collected by CDF and D0 experiments at the Fermilab Tevatron Collider. Earlier measurements from CDF and D0 are combined with the two latest, more precise measurements: a CDF measurement in the electron and muon channels using data corresponding to 2.2 fb(-1) of integrated luminosity, and a D0 measurement in the electron channel using data corresponding to 4.3 fb(-1) of integrated luminosity. The resulting Tevatron average for the mass of the W boson is M-W = 80387 +/- 16 MeV. Including measurements obtained in electron-positron collisions at LEP yields the most precise value of M-W = 80385 +/- 15 MeV.
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5.
  • Aaltonen, T., et al. (author)
  • Combination of measurements of the top-quark pair production cross section from the Tevatron Collider
  • 2014
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 89:7
  • Journal article (peer-reviewed)abstract
    • We combine six measurements of the inclusive top-quark pair (t(sic)) production cross section (sigma(t)(sic)) from data collected with the CDF and D0 detectors at the Fermilab Tevatron with proton-antiproton collisions at root s = 1.96 TeV. The data correspond to integrated luminosities of up to 8.8 fb(-1). We obtain a value of sigma tt = 7.60 +/- 0.41 pb for a top-quark mass of m(t) = 172.5 GeV. The contributions to the uncertainty are 0.20 pb from statistical sources, 0.29 pb from systematic sources, and 0.21 pb from the uncertainty on the integrated luminosity. The result is in good agreement with the standard model expectation of 7.35(-0.33)(+0.28) pb at next-to-next-to-leading order and next-to-next-to leading logarithms in perturbative QCD.
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6.
  • Aaltonen, T., et al. (author)
  • Observation of s-Channel Production of Single Top Quarks at the Tevatron
  • 2014
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 112:23
  • Journal article (peer-reviewed)abstract
    • We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb(-1) per experiment. The measured cross section is sigma(s) = 1.29(-0.24)(+0.26) pb. The probability of observing a statistical fluctuation of the background to a cross section of the observed size or larger is 1.8 x 10(-10), corresponding to a significance of 6.3 standard deviations for the presence of an s-channel contribution to the production of single-top quarks.
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7.
  • Aaltonen, T., et al. (author)
  • Higgs boson studies at the Tevatron
  • 2013
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052014-
  • Journal article (peer-reviewed)abstract
    • We combine searches by the CDF and D0 Collaborations for the standard model Higgs boson with mass in the range 90-200 GeV/c(2) produced in the gluon-gluon fusion, WH, ZH, t (t) over barH, and vector boson fusion processes, and decaying in the H -> b (b) over bar, H -> W+W-, H -> ZZ, H -> tau(+)tau(-), and H -> gamma gamma modes. The data correspond to integrated luminosities of up to 10 fb(-1) and were collected at the Fermilab Tevatron in p (p) over bar collisions at root s = 1.96 TeV. The searches are also interpreted in the context of fermiophobic and fourth generation models. We observe a significant excess of events in the mass range between 115 and 140 GeV/c(2). The local significance corresponds to 3.0 standard deviations at m(H) = 125 GeV/c(2), consistent with the mass of the Higgs boson observed at the LHC, and we expect a local significance of 1.9 standard deviations. We separately combine searches for H -> b (b) over bar, H -> W+W-, H -> tau(+)tau(-), and H -> gamma gamma. The observed signal strengths in all channels are consistent with the presence of a standard model Higgs boson with a mass of 125 GeV/c(2).
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8.
  • 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|.
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9.
  • Abazov, V. M., et al. (author)
  • Combination of searches for anomalous top quark couplings with 5.4 fb(-1) of p(p)over-bar collisions
  • 2012
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 713:3, s. 165-171
  • Journal article (peer-reviewed)abstract
    • We present measurements of the tWb coupling form factors using information from electroweak single top quark production and from the helicity of W bosons from top quark decays in t (t) over bar events. We set upper limits on anomalous tWb coupling form factors using data collected with the DO detector at the Tevatron p (p) over bar collider corresponding to an integrated luminosity of 5.4 fb(-1).
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10.
  • 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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11.
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12.
  • 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.
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13.
  • Abazov, V. M., et al. (author)
  • Measurement of spin correlation in t(t)over-bar production using dilepton final states
  • 2011
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 702:1, s. 16-23
  • Journal article (peer-reviewed)abstract
    • We measure the correlation between the spin of the top quark and the spin of the anti-top quark in t (t) over bar -> W(+)bW(-)(b) over bar -> l(+)vbl(-) (v) 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 is an electron or 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 correlation is extracted from the angles of the two leptons in the t and (t) over bar rest frames, yielding a correlation strength C = 0.10(-0.45)(+0.45). in agreement with the NLO QCD prediction within two standard deviations, but also in agreement with the no correlation hypothesis.
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14.
  • Abazov, V. M., et al. (author)
  • Measurement of the Lambda(0)(b) lifetime in the exclusive decay Lambda(0)(b) -> J/psi Lambda(0) in p(p)over-bar collisions at root s=1.96 TeV
  • 2012
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:11, s. 112003-
  • Journal article (peer-reviewed)abstract
    • We measure the Lambda(0)(b) lifetime in the fully reconstructed decay Lambda(0)(b) -> J/psi Lambda(0) using 10.4 fb(-1) of p (p) over bar collisions collected with the D0 detector at root s = 1.96 TeV. The lifetime of the topologically similar decay channel B-0 -> J/psi K-S(0) is also measured. We obtain tau(Lambda(0)(b)) = 1.303 +/- 0.075(stat) +/- 0.035(syst) ps and tau(B-0) = 1.508 +/- 0.025(stat) +/- 0.043(syst) ps. Using these measurements, we determine the lifetime ratio of tau(Lambda(0)(b))/tau(B-0) = 0.864 +/- 0.052(stat) +/- 0.033(syst).
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15.
  • Abazov, V. M., et al. (author)
  • Measurement of the photon plus b-jet production differential cross section in p(p)over-bar) collisions at root s=1.96 TeV
  • 2012
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 714:1, s. 32-39
  • Journal article (peer-reviewed)abstract
    • We present measurements of the differential cross section d sigma/dp(T)(gamma) for the inclusive production of a photon in association with a b-quark jet for photons with rapidities vertical bar y(gamma)vertical bar < 1.0 and 30 < p(T)(gamma) < 300 GeV, as well as for photons with 1.5 < vertical bar y(gamma)vertical bar < 2.5 and 30 < p(T)(gamma) < 200 GeV, where p(T)(gamma) is the photon transverse momentum. The b-quark jets are required to have p(T) > 15 GeV and rapidity vertical bar Y-jet vertical bar < 1.5. The results are based on data corresponding to an integrated luminosity of 8.7 fb(-1), recorded with the DO detector at the Fermilab Tevatron p<(p)over bar>) Collider at root s = 1.96 TeV. The measured cross sections are compared with next-to-leading order perturbative QCD calculations using different sets of parton distribution functions as well as to predictions based on the k(T)-factorization QCD approach, and those from the SHERPA and PYTHIA Monte Carlo event generators.
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16.
  • Abazov, V. M., et al. (author)
  • Measurement of the production fraction times branching fraction f(b -> Lambda(b)) . B(Lambda(b) -> J/psi Lambda)
  • 2011
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:3, s. 031102-
  • Journal article (peer-reviewed)abstract
    • The Lambda(b)(udb) baryon is observed in the decay Lambda(b) -> J/psi Lambda using 6.1fb(-1) of p (p) over bar collisions collected with the D0 detector at root s = 1/96 TeV. The production fraction multiplied by the branching fraction for this decay relative to that for the decay B(0) -> J/psi K(s)(0) is measured to be 0.345 +/- 0.034(stat) +/- 0.033(syst) +/- 0.003(PDG). Using the world average value of f(b -> B(0)) . B(B(0) -> J/psi K(s)(0) = (1.74 +/- 0.08) x 10(-5), we obtain f(b -> Lambda(b)) . B(Lambda(b) -> J/psi Lambda) = (6.01 +/- 0.60(stat) +/- 0.58(syst) +/- 0.28(PDG)) x 10(-5). This measurement represents an improvement in precision by about a factor of 3 with respect to the current world average.
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17.
  • 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.
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18.
  • Abazov, V. M., et al. (author)
  • Measurement of the W Boson Mass with the D0 Detector
  • 2012
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 108:15, s. 151804-
  • Journal article (peer-reviewed)abstract
    • We present a measurement of the W boson mass using data corresponding to 4: 3 fb(-1) of integrated luminosity collected with the D0 detector during Run II at the Fermilab Tevatron p (p) over tilde collider. With a sample of 1 677 394 W -> e nu candidate events, we measure M-W = 80.367 +/- 0.026 GeV. This result is combined with an earlier D0 result determined using an independent Run II data sample, corresponding to 1 fb(-1) of integrated luminosity, to yield MW 80.375 +/- 0.023 GeV.
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19.
  • 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.
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20.
  • 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.
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21.
  • 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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22.
  • Abazov, V. M., et al. (author)
  • Observation of a narrow mass state decaying into Y(1S)+gamma in p(p)over-bar collisions at root s=1.96 TeV
  • 2012
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:3, s. 031103-
  • Journal article (peer-reviewed)abstract
    • Using data corresponding to an integrated luminosity of 1.3 fb(-1), we observe a narrow mass state decaying into Gamma(1S) + gamma, where the Gamma(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551 +/- 0.014(stat) +/- 0.017(syst) GeV/c(2), which is consistent with that of the state recently observed by the ATLAS Collaboration.
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23.
  • 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).
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24.
  • 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.
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25.
  • 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.
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26.
  • Abazov, V. M., et al. (author)
  • Search for flavor changing neutral currents in decays of top quarks
  • 2011
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 701:3, s. 313-320
  • Journal article (peer-reviewed)abstract
    • We present a search for flavor changing neutral currents in decays of top quarks. The analysis is based on a search for (ℓ,ℓ′=e,μ) final states using 4.1 fb−1 of integrated luminosity of collisions at . We extract limits on the branching ratio B(t→Zq) (q=u,c quarks), assuming anomalous tuZ or tcZ couplings. We do not observe any sign of such anomalous coupling and set a limit of B<3.2% at 95% C.L.
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27.
  • Abazov, V. M., et al. (author)
  • Search for the standard model Higgs boson in tau lepton final states D0 Collaboration
  • 2012
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 714:2-5, s. 237-245
  • Journal article (peer-reviewed)abstract
    • We present a search for the standard model Higgs boson in final states with an electron or muon and a hadronically decaying tau lepton in association with zero, one, or two or more jets using data corresponding to an integrated luminosity of up to 7.3 fb(-1) collected with the D0 detector at the Fermilab Tevatron collider. The analysis is sensitive to Higgs boson production via gluon-gluon fusion, associated vector boson production, and vector boson fusion, and to Higgs boson decays to tau tau, WW, ZZ and b (b) over bar pairs. Observed (expected) limits are set on the ratio of 95% C.L. upper limits on the cross section times branching ratio, relative to those predicted by the Standard Model, of 22 (14) at a Higgs boson mass of 115 GeV and 6.8 (7.7) at 165 GeV.
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28.
  • Abazov, V. M., et al. (author)
  • Search for Violation of Lorentz Invariance in Top Quark Pair Production and Decay
  • 2012
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 108:26, s. 261603-
  • Journal article (peer-reviewed)abstract
    • Using data collected with the D0 detector at the Fermilab Tevatron Collider, corresponding to 5: 3 fb(-1) of integrated luminosity, we search for violation of Lorentz invariance by examining the t (t) over bar production cross section in lepton + jets final states. We quantify this violation using the standard-model extension framework, which predicts a dependence of the t (t) over bar production cross section on sidereal time as the orientation of the detector changes with the rotation of the Earth. Within this framework, we measure components of the matrices (c(Q))(mu nu 33) and (c(U))(mu nu 33) containing coefficients used to parametrize violation of Lorentz invariance in the top quark sector. Within uncertainties, these coefficients are found to be consistent with zero.
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29.
  • Abazov, V. M., et al. (author)
  • Search for WH associated production in p(p)over-bar collisions at root s=1.96 TeV
  • 2012
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:3, s. 032005-
  • Journal article (peer-reviewed)abstract
    • This report describes a search for associated production of W and Higgs bosons based on data corresponding to an integrated luminosity of L approximate to 5.3 fb(-1) collected with the D0 detector at the Fermilab Tevatron p (p) over bar Collider. Events containing a W -> l nu candidate (with l corresponding to e or mu) are selected in association with two or three reconstructed jets. One or two of the jets are required to be consistent with having evolved from a b quark. A multivariate discriminant technique is used to improve the separation of signal and backgrounds. Expected and observed upper limits are obtained for the product of the WH production cross section and branching ratios and reported in terms of ratios relative to the prediction of the standard model as a function of the mass of the Higgs boson (M-H). The observed and expected 95% C. L. upper limits obtained for an assumed M-H = 115 GeV are, respectively, factors of 4.5 and 4.8 larger than the value predicted by the standard model.
  •  
30.
  • Abazov, V. M., et al. (author)
  • Search for Z gamma events with large missing transverse energy in p(p)over-bar collisions at root s = 1.96 TeV
  • 2012
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:7, s. 071701-
  • Journal article (peer-reviewed)abstract
    • We present the first search for new phenomena in Z gamma final states with large missing transverse energy using data corresponding to an integrated luminosity of 6.2 fb(-1) collected with the D0 experiment in p (p) over bar collisions at root s 1.96 TeV. This signature is predicted in gauge-mediated supersymmetry-breaking models, where the lightest neutralino (chi) over tilde (0)(1) is the next-to-lightest supersymmetric particle and is produced in pairs, possibly through decay from heavier supersymmetric particles. The (chi) over tilde (0)(1) can decay either to a Z boson or a photon and an associated gravitino that escapes detection. We exclude this model at the 95% C.L. for supersymmetry-breaking scales of Lambda < 87 TeV.
  •  
31.
  • Abazov, V. M., et al. (author)
  • Study of the decay Bs0→J/ψf2′(1525) in μ +μ -K +K - final states
  • 2012
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:9, s. 092011-
  • Journal article (peer-reviewed)abstract
    • We investigate the decay Bs0→J/ψK +K - for invariant masses of the K +K - pair in the range 1.35<M(K +K -)<2GeV. The data sample corresponds to an integrated luminosity of 10.4fb -1 of pp̄ collisions at √s=1.96TeV accumulated with the D0 detector at the Fermilab Tevatron collider. From the study of the invariant mass and spin of the K +K - system, we find evidence for the two-body decay Bs0→J/ψf2′(1525) and measure the relative branching fraction of the decays Bs0→J/ψf2′(1525) and Bs0→J/ψ to be R f2′/=0.19±0.05(stat)±0.04(syst).
  •  
32.
  • 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).
  •  
33.
  • Abazov, V. M., et al. (author)
  • Combined search for the Higgs boson with the D0 experiment
  • 2013
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052011-
  • Journal article (peer-reviewed)abstract
    • We perform a combination of searches for standard model Higgs boson production in p (p) over bar collisions recorded by the D0 detector at the Fermilab Tevatron Collider at a center of mass energy of root s = 1.96 TeV. The different production and decay channels have been analyzed separately, with integrated luminosities of up to 9.7 fb(-1) and for Higgs boson masses 90 <= M-H <= 200 GeV. We combine these final states to achieve optimal sensitivity to the production of the Higgs boson. We also interpret the combination in terms of models with a fourth generation of fermions, and models with suppressed Higgs boson couplings to fermions. The result excludes a standard model Higgs boson at 95% C.L. in the ranges 90 < M-H < 101 GeV and 157 < M-H < 178 GeV, with an expected exclusion of 155 < M-H < 175 GeV. In the range 120 < M-H < 145 GeV, the data exhibit an excess over the expected background of up to 2 standard deviations, consistent with the presence of a standard model Higgs boson of mass 125 GeV.
  •  
34.
  • Abazov, V. M., et al. (author)
  • Combined Search for the Standard Model Higgs Boson Decaying to b(b)over-bar Using the D0 Run II Data Set
  • 2012
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:12, s. 121802-
  • Journal article (peer-reviewed)abstract
    • We present the results of the combination of searches for the standard model Higgs boson produced in association with a W or Z boson and decaying into b (b) over bar using the data sample collected with the D0 detector in p (p) over bar collisions at root s = 1.96 TeV at the Fermilab Tevatron Collider. We derive 95% C.L. upper limits on the Higgs boson cross section relative to the standard model prediction in the mass range 100 GeV <= M-H <= 150 GeV, and we exclude Higgs bosons with masses smaller than 102 GeV at the 95% C.L. In the mass range 120 GeV <= M-H <= 145 GeV, the data exhibit an excess above the background prediction with a global significance of 1.5 standard deviations, consistent with the expectation in the presence of a standard model Higgs boson.
  •  
35.
  • Abazov, V. M., et al. (author)
  • Constraints on Models for the Higgs Boson with Exotic Spin and Parity in VH -> Vb(b)over-bar Final States
  • 2014
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 113:16, s. 161802-
  • Journal article (peer-reviewed)abstract
    • We present constraints on models containing non-standard-model values for the spin J and parity P of the Higgs boson H in up to 9.7 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. These are the first studies of Higgs boson J(P) with fermions in the final state. In the ZH -> llb (b) over bar, WH -> l nu b (b) over barb, and ZH -> nu nu b (b) over bar final states, we compare the standard model (SM) Higgs boson prediction, J(P) = 0(+), with two alternative hypotheses, J(P) = 0(-) and J(P) = 2(+). We use a likelihood ratio to quantify the degree to which our data are incompatible with non-SM J(P) predictions for a range of possible production rates. Assuming that the production rate in the signal models considered is equal to the SM prediction, we reject the J(P) = 0(-) and J(P) = 2(+) hypotheses at the 97.6% CL and at the 99.0% CL, respectively. The expected exclusion sensitivity for a J(P) = 0(-)(J(P) = 2(+)) state is at the 99.86% (99.94%) CL. Under the hypothesis that our data are the result of a combination of the SM-like Higgs boson and either a J(P) = 0(-) or a J(P) = 2(+) signal, we exclude a J(P) = 0(-) fraction above 0.80 and a JP = 2(+) fraction above 0.67 at the 95% CL. The expected exclusion covers J(P) = 0(-)(J(P) = 2(+)) fractions above 0.54 (0.47).
  •  
36.
  • 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.
  •  
37.
  • Abazov, V. M., et al. (author)
  • Double parton interactions in gamma+3 jet and gamma plus b/c jet+2 jet events in p(p)over-bar collisions at root s=1.96 TeV
  • 2014
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 89:7, s. 072006-
  • Journal article (peer-reviewed)abstract
    • We determine the fraction of events with double parton (DP) Scattering in a single p (p) over bar collisions at root s = 1.96 TeV in gamma + 3 jet and gamma + b/c jet + 2 jet events collected with the D0 detector and corresponding to an integrated luminosity of about 8.7 fb(-1). The DP fractions and effective cross sections (sigma(eff)) are measured for both event samples using the same kinematic selections. The measured DP fractions range from 0.21 to 0.17, with effective cross sections in the gamma + 3 jet and gamma + b/cjet + 2 jet samples of sigma(incl)(eff) = 12.7 +/- 0.2(stat) +/- 1.3(syst) mb and sigma(HF)(eff) = 14.6 +/- 0.6(stat) +/- 3.2(syst) mb, respectively.
  •  
38.
  • Abazov, V. M., et al. (author)
  • Electron and photon identification in the Do experiment
  • 2014
  • In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 750, s. 78-95
  • Journal article (peer-reviewed)abstract
    • The electron and photon reconstruction and identification algorithms used by the DO Collaboration at the Fermilab Tevatron collider are described. The determination of the electron energy scale and resolution is presented. Studies of the performance of the electron and photon reconstruction and identification are summarized. The results are based on measurements of Z boson decay events of Z ee and Z gamma ll(i=e mu) collected in pp(over bar) collisions at a center- of- mass energy of 1.96 TeV using an integrated luminosity of up to10 fb(-1.)
  •  
39.
  • Abazov, V. M., et al. (author)
  • Evidence for s-channel single top quark production in p(p)over-bar collisions at root s=1.96 TeV
  • 2013
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 726:4-5, s. 656-664
  • Journal article (peer-reviewed)abstract
    • We present measurements of the cross sections for the two main production modes of single top quarks in p (p) over bar collisions at root s = 1.96 TeV in the Run II data collected with the DO detector at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 9.7 fb(-1). The s-channel cross section is measured to be sigma(p (p) over bar -> tb + X) = 1.10(-0.31)(+0.33) pb with no assumptions on the value of the t-channel cross section. Similarly, the t-channel cross section is measured to be sigma(p (p) over bar -> tqb + X) = 3.07(-0.49)(+0.54) pb. We also measure the s + t combined cross section as sigma(p (p) over bar -> tb + X, tqb + X) = 4.11(-0.55)(+0.60) ph and set a lower limit on the CKM matrix element vertical bar V-tb vertical bar> 0.92 at 95% C.L., assuming mt = 172.5 GeV. The probability to measure a cross section for the s channel at the observed value or higher in the absence of signal is 1.0 x 10(-4), corresponding to a significance of 3.7 standard deviations. 
  •  
40.
  • Abazov, V. M., et al. (author)
  • Evidence for Spin Correlation in t(t)over-bar Production
  • 2012
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 108:3, s. 032004-
  • Journal article (peer-reviewed)abstract
    • We present a measurement of the ratio of events with correlated t and (t) over bar spins to the total number of t (t) over bar events. This ratio f is evaluated using a matrix-element-based approach in 729 t (t) over bar candidate events with a single lepton l (electron or muon) and at least four jets. The analyzed p (p) over bar collisions data correspond to an integrated luminosity of 5: 3 fb(-1) and were collected with the D0 detector at the Fermilab Tevatron collider operating at a center-of-mass energy root s = 1.96 TeV. Combining this result with a recent measurement of f in dileptonic final states, we find f in agreement with the standard model. In addition, the combination provides evidence for the presence of spin correlation in t (t) over bar events with a significance of more than 3 standard deviations.
  •  
41.
  • 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.
  •  
42.
  • Abazov, V. M., et al. (author)
  • Improved b quark jet identification at the D0 experiment
  • 2014
  • In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 763, s. 290-303
  • Journal article (peer-reviewed)abstract
    • The ability to identify jets which originated from b quarks is an important tool of the physics program of the D0 experiment at the Fermilab Tevatron p (p) over bar collider. This paper describes a new algorithm designed to select jets originating from b quarks while suppressing the contamination caused by jets from other quark flavors and gluons. Additionally, a new technique, the SystemN method, for determining the misidentification rate directly from data is presented. (C) 2014 Elsevier B.V. All rights reserved.
  •  
43.
  • 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.
  •  
44.
  • Abazov, V. M., et al. (author)
  • Jet energy scale determination in the DO experiment
  • 2014
  • In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 763, s. 442-475
  • Journal article (peer-reviewed)abstract
    • The calibration of jet energy measured in the DO detector is presented, based on p (p) over bar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider, jet energies are measured using a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively. This paper describes the energy calibration of jets performed with gamma+jet, Z+jet and dilet events, with jet transverse momentum p(T) > 6 GeV and pseudorapidity range vertical bar eta vertical bar < 3.6, The corrections are measured separately for data and simulation, achieving a precision of 1.4-1.8% for jets in the central part of the calorimeter ancl up to 3.5% for the jets with pseudorapidity vertical bar eta vertical bar = 3.0. Specific corrections are extracted to enhance the description of jet energy in simulation and in particular of the effects due to the flavor of the parton originating the jet, correcting biases up to 3-4% in jets with low PT originating from gluons and up to 6-8% in jets from b quarks. Published by Elsevier B.V.
  •  
45.
  • Abazov, V. M., et al. (author)
  • Limits on anomalous trilinear gauge boson couplings from WW, WZ and Wγ production in pp- collisions at √s=1.96TeV
  • 2012
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 718:2, s. 451-459
  • Journal article (peer-reviewed)abstract
    • We present searches for the anomalous γWW and ZWW trilinear gauge boson couplings from WW and WZ production using lepton plus dijet final states and a combination with results from Wγ, WW, and WZ production with leptonic final states. The analyzed data correspond to up to 8.6fb -1 of integrated luminosity collected by the D0 detector in pp- collisions at s=1.96TeV. We set the most stringent limits at a hadron collider to date assuming two different relations between the anomalous coupling parameters δκ γ, λ, and δg1Z for a cutoff energy scale Λ=2TeV. The combined 68% C.L. limits are -0.057<δκ γ<0.154, -0.015<λ<0.028, and -0.008<δg1Z<0.054 for the LEP parameterization, and -0.007<δκ<0.081 and -0.017<λ<0.028 for the equal couplings parameterization. We also present the most stringent limits of the W boson magnetic dipole and electric quadrupole moments.
  •  
46.
  • Abazov, V. M., et al. (author)
  • Measurement of angular correlations of jets at s=1.96 TeV and determination of the strong coupling at high momentum transfers
  • 2012
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 718:1, s. 56-63
  • Journal article (peer-reviewed)abstract
    • We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance δR in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of δR and for different transverse momentum requirements for the neighboring jets. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb -1 collected with the D0 detector at the Fermilab Tevatron Collider in pp- collisions at s=1.96 TeV. The results are well described by a perturbative QCD calculation in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects. From these results, we extract the strong coupling and test the QCD predictions for its running over a range of momentum transfers of 50-400 GeV.
  •  
47.
  • Abazov, V. M., et al. (author)
  • Measurement of Associated Production of Z Bosons with Charm Quark Jets in p(p)over-bar Collisions at root s = 1.96 TeV
  • 2014
  • In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 112:4, s. 042001-
  • Journal article (peer-reviewed)abstract
    • We present the first measurements of the ratios of cross sections sigma(p (p) over bar -> Z + c jet)/sigma(p (p) over bar -> Z + jet) and sigma(p (p) over bar -> Z + jet)/sigma(p (p) over bar -> Z + b jet) for the associated production of a Z boson with at least one charm or bottom quark jet. Jets have transverse momentum p(T)(jet) > 20 GeV and pseudorapidity vertical bar eta(jet)vertical bar < 2.5. These cross section ratios are measured differentially as a function of jet and Z boson transverse momenta, based on 9.7 fb(-1) of p<(p)over bar> collisions collected with the D0 detector at the Fermilab Tevatron Collider at root s = 1.96 TeV. The measurements show significant deviations from perturbative QCD calculations and predictions from various event generators.
  •  
48.
  • Abazov, V. M., et al. (author)
  • Measurement of differential tt production cross sections in pp collisions
  • 2014
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 90:9, s. 092006-
  • Journal article (peer-reviewed)abstract
    • The production of top quark-antiquark pair events in pp collisions at root s= 1.96 TeV is studied as a function of the transverse momentum and absolute value of the rapidity of the top quarks as well as of the invariant mass of the tt pair. We select events containing an isolated lepton, a large imbalance in transverse momentum, and four or more jets with at least one jet identified as originating from a b quark. The data sample corresponds to 9.7 fb(-1) of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Observed differential cross sections are consistent with standard model predictions.
  •  
49.
  • Abazov, V. M., et al. (author)
  • Measurement of leptonic asymmetries and top-quark polarization in t(t)over-bar production
  • 2013
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 87:1, s. 011103-
  • Journal article (peer-reviewed)abstract
    • We present measurements of lepton (l) angular distributions in top-quark (t) pair production and t (t) over bar -> W(+)bW-(b) over bar -> l(+) vbl-(v) over bar(b) over bar decays produced in p (p) over bar collisions at a center-of-mass energy of root s = 1.96 TeV, where l is an electron or muon. Using data corresponding to an integrated luminosity of 5.4 fb(-1), collected with the D0 detector at the Fermilab Tevatron Collider, we measure for the first time the leptonic forward-backward asymmetry in dilepton final states and obtain A(FB)(l) = (5.8 +/- 5.1(stat) +/- 1.3(syst))%, corrected for detector acceptance. This is compared to the standard model prediction of A(FB)(l)(predicted) = (4.7 +/- 0.1)%. A deviation from the standard model prediction as previously seen in a D0 measurement based on the analysis of the l + jets final state is not observed in these dilepton final states. The two results differ from each other by 1.4 standard deviations and are combined to obtain A(FB)(l) = (11.8 +/- 3.2)%. Furthermore, we present a first study of the top-quark polarization.
  •  
50.
  • 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.
  •  
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