| 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 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- 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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| 10. |
- 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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