| 1. |
- Aaltonen, T., et al.
(författare)
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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
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:7, s. 071804-
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Aaltonen, T., et al.
(författare)
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Combination of CDF and D0 measurements of the W boson helicity in top quark decays
- 2012
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:7, s. 071106-
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Tidskriftsartikel (refereegranskat)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. |
- Abazov, V. M., et al.
(författare)
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Search for flavor changing neutral currents in decays of top quarks
- 2011
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 701:3, s. 313-320
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Abazov, V. M., et al.
(författare)
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Measurement of spin correlation in t(t)over-bar production using dilepton final states
- 2011
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 702:1, s. 16-23
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Abazov, V. M., et al.
(författare)
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Measurement of the t(t)over-bar production cross section using dilepton events in p(p)over-bar collisions
- 2011
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:5, s. 403-410
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Abazov, V. M., et al.
(författare)
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Search for the standard model Higgs boson in the ZH -> nu(nu)over-barb(b)over-bar channel in 9.5 fb(-1) of p(p)over-bar collisions at root s=1.96 TeV
- 2012
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 716:2, s. 285-293
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Tidskriftsartikel (refereegranskat)abstract
- We present a search for the standard model Higgs boson in 9.5 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 contains a pair of b jets and is characterized by an imbalance in transverse energy, as expected from p (p) over bar -> ZH -> nu(nu) over barb (b) over bar production. The search is also sensitive to the WH -> l nu b (b) over bar channel when the charged lepton is not identified. The data are found to be in good agreement with the expected background. For a Higgs boson mass of 125 GeV, we set a limit at the 95% C.L. on the cross section sigma(p (p) over bar -> vertical bar Z/W vertical bar H), assuming standard model branching fractions, that is a factor of 4.3 times larger than the theoretical standard model value, while the expected factor is 3.9. The search is also used to measure a combined WZ and ZZ production cross section that is a factor of 0.94 +/- 0.31 (stat) +/- 0.34 (syst) times the standard model prediction of 4.4 pb, with an observed significance of 2.0 standard deviations. (C) 2012 Elsevier B.V. All rights reserved.
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| 7. |
- Abazov, V. M., et al.
(författare)
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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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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 704:5, s. 434-441
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Abazov, V. M., et al.
(författare)
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Combination of searches for anomalous top quark couplings with 5.4 fb(-1) of p(p)over-bar collisions
- 2012
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 713:3, s. 165-171
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Abazov, V. M., et al.
(författare)
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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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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 703:4, s. 422-427
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Abazov, V. M., et al.
(författare)
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Measurement of the photon plus b-jet production differential cross section in p(p)over-bar) collisions at root s=1.96 TeV
- 2012
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 714:1, s. 32-39
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Tidskriftsartikel (refereegranskat)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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| 11. |
- Abazov, V. M., et al.
(författare)
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Measurement of the ZZ production cross section in p(p)over-bar collisions at root s=1.96 TeV
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:1, s. 011103-
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Tidskriftsartikel (refereegranskat)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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| 12. |
- Abazov, V. M., et al.
(författare)
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Model-independent measurement of t-channel single top quark production in p(p)over-bar collisions at,root s=1.96 TeV
- 2011
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 705:4, s. 313-319
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Tidskriftsartikel (refereegranskat)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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| 13. |
- Abazov, V. M., et al.
(författare)
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Search for the standard model Higgs boson in tau lepton final states D0 Collaboration
- 2012
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 714:2-5, s. 237-245
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Tidskriftsartikel (refereegranskat)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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| 14. |
- Abazov, V. M., et al.
(författare)
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Bounds on an Anomalous Dijet Resonance in W plus jets Production in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:1, s. 011804-
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Tidskriftsartikel (refereegranskat)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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| 15. |
- Abazov, V. M., et al.
(författare)
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Combined search for the Higgs boson with the D0 experiment
- 2013
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052011-
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Tidskriftsartikel (refereegranskat)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.
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| 16. |
- Abazov, V. M., et al.
(författare)
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Combined Search for the Standard Model Higgs Boson Decaying to b(b)over-bar Using the D0 Run II Data Set
- 2012
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:12, s. 121802-
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Tidskriftsartikel (refereegranskat)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.
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| 17. |
- Abazov, V. M., et al.
(författare)
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Direct measurement of the mass difference between top and antitop quarks
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:5, s. 052005-
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Tidskriftsartikel (refereegranskat)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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| 18. |
- Abazov, V. M., et al.
(författare)
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Evidence for Spin Correlation in t(t)over-bar Production
- 2012
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 108:3, s. 032004-
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Tidskriftsartikel (refereegranskat)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.
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| 19. |
- Abazov, V. M., et al.
(författare)
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Forward-backward asymmetry in top quark-antiquark production
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:11, s. 112005-
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Tidskriftsartikel (refereegranskat)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.
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| 20. |
- Abazov, V. M., et al.
(författare)
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Improved determination of the width of the top quark
- 2012
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:9, s. 091104-
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Tidskriftsartikel (refereegranskat)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.
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| 21. |
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| 22. |
- Abazov, V. M., et al.
(författare)
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Measurement of Spin Correlation in t(t)over-bar Production Using a Matrix Element Approach
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:3, s. 032001-
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Tidskriftsartikel (refereegranskat)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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| 23. |
- Abazov, V. M., et al.
(författare)
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Measurement of the anomalous like-sign dimuon charge asymmetry with 9 fb(-1) of p(p)over-bar collisions
- 2011
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:5, s. 052007-
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Tidskriftsartikel (refereegranskat)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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| 24. |
- Abazov, V. M., et al.
(författare)
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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
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:3, s. 032006-
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Tidskriftsartikel (refereegranskat)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%.
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| 25. |
- Abazov, V. M., et al.
(författare)
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Measurement of the differential cross sections for isolated direct photon pair production in p(p)over-bar collisions at root s=1.96 TeV
- 2013
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 725:1-3, s. 6-14
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of direct photon pair production cross sections using 8.5 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron p (p) over bar collider. The results are presented as differential distributions of the photon pair invariant mass d sigma/dM(gamma gamma), pair transverse momentum d sigma/dp(T)(gamma gamma) azimuthal angle between the photons d sigma/d Delta(phi)(gamma gamma), and polar scattering angle in the Collins-Soper frame d sigma/d vertical bar cos theta*vertical bar. Measurements are performed for isolated photons with transverse momenta p(T)(gamma) > 18 (17) GeV for the leading (next-to-leading) photon in P-T, pseudorapidities vertical bar eta(gamma)vertical bar < 0.9, and a separation in eta-phi space Delta R-gamma gamma > 0.4. We present comparisons with the predictions from Monte Carlo event generators DIPHOX and RESBOS implementing QCD calculations at next-to-leading order, 2 gamma NNLO at next-to-next-to-leading order, and SHERPA using matrix elements with higher-order real emissions matched to parton shower.
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