| 1. |
- 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
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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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| 2. |
- Abazov, V. M., et al.
(author)
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Determination of the Width of the Top Quark
- 2011
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:2, s. 022001-
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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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| 3. |
- Abazov, V. M., et al.
(author)
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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
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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.
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| 4. |
- 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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| 5. |
- 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
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:12, s. 122001-
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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.
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| 6. |
- Abazov, V. M., et al.
(author)
-
Search for pair production of the scalar top quark in the electron plus muon final state
- 2011
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 696:4, s. 321-327
-
Journal article (peer-reviewed)abstract
- We report the result of a search for the pair production of the lightest supersymmetric partner of the top quark ((t) over tilde (1)) in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider corresponding to an integrated luminosity of 5.4 fb(-1). The scalar top quarks are assumed to decay into a b quark, a charged lepton, and a scalar neutrino ((nu) over bar). and the search is performed in the electron plus muon final state. No significant excess of events above the standard model prediction is detected, and substantially improved exclusion limits at the 95% C.L. are set in the the (M-(t) over tilde1, M-(nu) over tilde mass plane.
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| 7. |
- Abazov, V. M., et al.
(author)
-
Search for Resonant WW and WZ 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. 011801-
-
Journal article (peer-reviewed)abstract
- We search for resonant WW or WZ production by using up to 5: 4 fb(-1) of integrated luminosity collected by the D0 experiment in run II of the Fermilab Tevatron Collider. The data are consistent with the standard model background expectation, and we set limits on a resonance mass by using the sequential standard model W' boson and the Randall-Sundrum model graviton G as benchmarks. We exclude a sequential standard model W' boson in the mass range 180-690 GeV and a Randall-Sundrum graviton in the range 300-754 GeV at 95% C. L.
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| 8. |
- Abazov, V. M., et al.
(author)
-
Search for Single Vectorlike Quarks in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:8, s. 081801-
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Journal article (peer-reviewed)abstract
- We present a search for hypothetical vectorlike quarks in p (p) over bar collisions at root s = 1.96 TeV. The data were collected by the D0 detector at the Fermilab Tevatron Collider and correspond to an integrated luminosity of 5.4 fb(-1). We select events with a final state composed of a W or Z boson and a jet consistent with a heavy object decay. We observe no significant excess in comparison to the background prediction and set limits on production cross sections for vectorlike quarks decaying to W + jet and Z + jet. These are the most stringent limits to date for electroweak single vectorlike quark production at hadron colliders.
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| 9. |
- Abazov, V. M., et al.
(author)
-
Azimuthal decorrelations and multiple parton interactions in gamma+2 jet and gamma+3 jet events in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 83:5, s. 052008-
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Journal article (peer-reviewed)abstract
- Samples of inclusive gamma + 2 jet and gamma + 3 jet events collected by the D0 experiment with an integrated luminosity of about 1 fb(-1) in p (p) over bar collisions at root s = 1.96 TeV are used to measure cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (p(T)) of the gamma + leading jet system (jets are ordered in p(T)) and p(T) of the other jet for gamma + 2 jet, or p(T) sum of the two other jets for gamma + 3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo (MC) generators. The data indicate a contribution from events with double parton (DP) interactions and are well-described by predictions provided by the PYTHIA MPI models with p(T)-ordered showers and by SHERPA with the default MPI model. The gamma + 2 jet data are also used to determine the fraction of events with DP interactions as a function of the azimuthal angle and as a function of the second jet p(T).
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| 10. |
- Abazov, V. M., et al.
(author)
-
Measurement of color flow in t(t)over-bar events from p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 83:9, s. 092002-
-
Journal article (peer-reviewed)abstract
- We present the first measurement of the color representation of the hadronically decaying W boson in t (t) over bar events, from 5.3 fb(-1) of integrated luminosity collected with the D0 experiment. A novel calorimeter-based vectorial variable, "jet pull," is used, sensitive to the color-flow structure of the final state. We find that the fraction of uncolored W bosons is 0.56 +/- 0.42(stat + syst), in agreement with the standard model.
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| 11. |
- Abazov, V. M., et al.
(author)
-
Measurement of the top quark pair production cross section in the lepton plus jets channel in proton-antiproton collisions at root s=1.96 TeV
- 2011
-
In: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:1, s. 012008-
-
Journal article (peer-reviewed)abstract
- We present a measurement of the inclusive top quark pair production cross section in p (p) over bar collisions at root s = 1.96 TeV utilizing data corresponding to an integrated luminosity of 5.3 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing one high-p(T) isolated electron or muon and at least two jets, and we perform three analyses: one exploiting specific kinematic features of t (t) over bar events, the second using b-jet identification, and the third using both techniques to separate the t (t) over bar signal from the background. In the third case, we determine simultaneously the t (t) over bar cross section and the ratio of the production rates of W + heavy flavor jets and W + light flavor jets, which reduces the impact of the systematic uncertainties related to the background estimation. Assuming a top quark mass of 172.5 GeV, we obtain sigma(t (t) over bar) = 7.78(-0.64)(-0.77)pb. This result agrees with predictions of the standard model.
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| 12. |
- Abazov, V. M., et al.
(author)
-
Measurement of the W boson helicity in top quark decays using 5.4 fb(-1) of p(p)over-bar collision data
- 2011
-
In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 83:3, s. 032009-
-
Journal article (peer-reviewed)abstract
- We present a measurement of the helicity of the W boson produced in top quark decays using t (t) over bar decays in the l + jets and dilepton final states selected from a sample of 5.4 fb(-1) of collisions recorded using the D0 detector at the Fermilab Tevatron p (p) over bar collider. We measure the fractions of longitudinal and right-handed W bosons to be f(0) = 0.669 +/- 0.102[+/- 0.078(stat.) +/- 0.065(syst.) +/- and f(+) = 0.023 +/- 0.053[+/- 0.041(stat.) +/- 0.034(syst.)], respectively. This result is consistent at the 98% level with the standard model. A measurement with f(0) fixed to the value from the standard model yields f(+) = 0.010 +/- 0.037[+/- 0.022(stat.) +/- 0.030(syst.).].
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| 13. |
- Abazov, V. M., et al.
(author)
-
Search for neutral Higgs bosons in the multi-b-jet topology in 5.2 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. ; 698:2, s. 97-104
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Journal article (peer-reviewed)abstract
- Data recorded by the DO experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. The search is performed in the three-b-quark channel using multijet-triggered events corresponding to an integrated luminosity of 5.2 fb(-1). In the absence of any significant excess above background, limits are set on the cross section multiplied by the branching ratio in the Higgs boson mass range 90 to 300 GeV, extending the excluded regions in the parameter space of the minimal supersymmetric standard model. (C) 2011 Elsevier B.V. All rights reserved.
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| 14. |
- Abazov, V. M., et al.
(author)
-
Search for the Standard Model Higgs Boson in the H -> WW -> lvq '(q)over-bar Decay Channel
- 2011
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:17, s. 171802-
-
Journal article (peer-reviewed)abstract
- We present a search for the standard model Higgs boson (H) in p (p) over bar collisions at root s = 1.96 TeV in events containing a charged lepton (l), missing transverse energy, and at least two jets, using 5.4 fb(-1) of integrated luminosity recorded with the D0 detector at the Fermilab Tevatron Collider. This analysis is sensitive primarily to Higgs bosons produced through the fusion of two gluons or two electroweak bosons, with subsequent decay H -> WW -> lvq'(q) over bar, where l is an electron or muon. The search is also sensitive to contributions from other production channels, such as WH -> lvb (b) over bar. In the absence of a signal, we set limits at the 95% C.L. on the cross section for H production sigma(p (p) over bar -> H + X) in these final states. For a mass of M-H = 160 GeV, the limit is a factor of 3.9 larger than the cross section in the standard model and consistent with an a priori expected sensitivity of 5.0.
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| 15. |
- Abazov, V. M., et al.
(author)
-
Search for W H associated production in 5.3 fb(-1) of p(p)over-bar collisions at the Fermilab Tevatron
- 2011
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 698:1, s. 6-13
-
Journal article (peer-reviewed)abstract
- We present a search for associated production of Higgs and W bosons in p (p) over bar collisions at a center of mass energy of root s = 1.96 TeV in 5.3 fb(-1) of integrated luminosity recorded by the DO experiment. Multivariate analysis techniques are applied to events containing one lepton, an imbalance in transverse energy, and one or two b-tagged jets to discriminate a potential WH signal from Standard Model backgrounds. We observe good agreement between data and expected backgrounds, and set an upper limit of 4.5 (at 95% confidence level and for m(H) = 115 GeV) on the ratio of the WH cross section multiplied by the branching fraction of H -> b (b) over bar to its Standard Model prediction, which is consistent with an expected limit of 4.8.
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| 16. |
- Abazov, V. M., et al.
(author)
-
Search for W' -> tb resonances with left- and right-handed couplings to fermions D0 Collaboration
- 2011
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 699:3, s. 145-150
-
Journal article (peer-reviewed)abstract
- We present a search for the production of a heavy gauge boson, W', that decays to third-generation quarks, by DO Collaboration in p (p) over bar) collisions at root s = 1.96 TeV. We set 95% confidence level upper limits on the production cross section times branching fraction. For the first time, we set limits for arbitrary combinations of left-and right-handed couplings of the W' boson to fermions. For couplings with the same strength as for the standard model W boson, we set the following limits, assuming that there are right-handed neutrinos nu(R) for all three generations with M(W') > m(nu(R)): M(W') > 863 GeV for purely left-handed couplings, M(W') > 885 GeV for purely right-handed couplings, and M(W') > 916 GeV if both left-and right-handed couplings are present. The limit for right-handed couplings improves for M(W') < m(nu(R)) to M(W') > 890 GeV.
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| 17. |
- Abazov, V. M., et al.
(author)
-
Measurement of the ratio of inclusive cross sections sigma(p(p)over-bar -> Z plus b-quark jet)/sigma(p(p)over-bar -> Z plus jet) at root s=1.96 TeV
- 2011
-
In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 83:3, s. 031105-
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Journal article (peer-reviewed)abstract
- The ratio of the cross section for p (p) over bar interactions producing a Z boson and at least one b-quark jet to the inclusive Z + jet cross section is measured using 4.2 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 Z -> l(+) l- candidate events with at least one b jet are discriminated from Z + charm and light jet(s) events by a novel technique that exploits the properties of the tracks associated to the jet. The measured ratio is 0: 0193 +/- 0: 0027 for events having a jet with transverse momentum p(T) > 20 GeV and pseudorapidity vertical bar eta vertical bar <= 2.5, which is the most precise to date and is consistent with theoretical predictions.
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| 18. |
- Abazov, V. M., et al.
(author)
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Determination of the pole and (MS)over-bar masses of the top quark from the t(t)over-bar cross section
- 2011
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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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| 19. |
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| 20. |
- 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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| 21. |
- 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
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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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| 22. |
- 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-
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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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| 23. |
- 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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| 24. |
- 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-
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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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| 25. |
- Abazov, V. M., et al.
(author)
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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
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:5, s. 434-441
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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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