| 1. |
- Aad, G, et al.
(författare)
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Searches for scalar leptoquarks in pp collisions at [Formula: see text] = 8 TeV with the ATLAS detector.
- 2016
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 76
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Tidskriftsartikel (refereegranskat)abstract
- Searches for pair-produced scalar leptoquarks are performed using 20 fb[Formula: see text] of proton-proton collision data provided by the LHC and recorded by the ATLAS detector at [Formula: see text] TeV. Events with two electrons (muons) and two or more jets in the final state are used to search for first (second)-generation leptoquarks. The results from two previously published ATLAS analyses are interpreted in terms of third-generation leptoquarks decaying to [Formula: see text] and [Formula: see text] final states. No statistically significant excess above the Standard Model expectation is observed in any channel and scalar leptoquarks are excluded at 95 % CL with masses up to [Formula: see text] 1050 GeV for first-generation leptoquarks, [Formula: see text] 1000 GeV for second-generation leptoquarks, [Formula: see text] 625 GeV for third-generation leptoquarks in the [Formula: see text] channel, and 200 [Formula: see text] 640 GeV in the [Formula: see text] channel.
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| 2. |
- Aad, G, et al.
(författare)
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Measurements of fiducial cross-sections for [Formula: see text] production with one or two additional b-jets in pp collisions at [Formula: see text]=8 TeV using the ATLAS detector.
- 2016
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 76
-
Tidskriftsartikel (refereegranskat)abstract
- Fiducial cross-sections for [Formula: see text] production with one or two additional b-jets are reported, using an integrated luminosity of 20.3 fb[Formula: see text] of proton-proton collisions at a centre-of-mass energy of 8 TeV at the Large Hadron Collider, collected with the ATLAS detector. The cross-section times branching ratio for [Formula: see text] events with at least one additional b-jet is measured to be 950 [Formula: see text] 70 (stat.) [Formula: see text] (syst.) fb in the lepton-plus-jets channel and 50 [Formula: see text] 10 (stat.) [Formula: see text] (syst.) fb in the [Formula: see text] channel. The cross-section times branching ratio for events with at least two additional b-jets is measured to be 19.3 [Formula: see text] 3.5 (stat.) [Formula: see text] 5.7 (syst.) fb in the dilepton channel ([Formula: see text], [Formula: see text], and ee) using a method based on tight selection criteria, and 13.5 [Formula: see text] 3.3 (stat.) [Formula: see text] 3.6 (syst.) fb using a looser selection that allows the background normalisation to be extracted from data. The latter method also measures a value of 1.30 [Formula: see text] 0.33 (stat.) [Formula: see text] 0.28 (syst.)% for the ratio of [Formula: see text] production with two additional b-jets to [Formula: see text] production with any two additional jets. All measurements are in good agreement with recent theory predictions.
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| 3. |
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| 4. |
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| 5. |
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| 6. |
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| 7. |
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| 8. |
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Aad, G., et al.
(författare)
-
- 2015
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Tidskriftsartikel (refereegranskat)
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Aad, G., et al.
(författare)
-
- 2016
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Ingår i: The European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6052. ; 76:1
-
Tidskriftsartikel (refereegranskat)
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| 17. |
- Aad, G., et al.
(författare)
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- 2015
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Tidskriftsartikel (refereegranskat)
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| 18. |
- Aad, G., et al.
(författare)
-
- 2015
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Ingår i: The European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6052. ; 75:9
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Tidskriftsartikel (refereegranskat)
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| 19. |
- Aad, G., et al.
(författare)
-
- 2015
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Ingår i: Journal of High Energy Physics. - : Springer. - 1029-8479 .- 1126-6708. ; :12
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Tidskriftsartikel (refereegranskat)
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| 20. |
- Aad, G., et al.
(författare)
-
- 2016
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Ingår i: Journal of High Energy Physics. - : Springer. - 1029-8479 .- 1126-6708. ; :1
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Tidskriftsartikel (refereegranskat)
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| 21. |
- Aad, G., et al.
(författare)
-
- 2016
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Ingår i: Physical Review D. Particles and fields. - : American Physical Society. - 0556-2821 .- 1089-4918. ; 93:1
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Tidskriftsartikel (refereegranskat)
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| 22. |
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| 23. |
- Aad, G., et al.
(författare)
-
- 2015
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Ingår i: Physical Review D. Particles and fields. - : American Physical Society. - 0556-2821 .- 1089-4918. ; 92:9
-
Tidskriftsartikel (refereegranskat)
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| 24. |
- Aad, G., et al.
(författare)
-
- 2015
-
Ingår i: Physical Review D. Particles and fields. - : American Physics Society. - 0556-2821 .- 1089-4918. ; 92:11
-
Tidskriftsartikel (refereegranskat)
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| 25. |
- Aad, G., et al.
(författare)
-
- 2015
-
Ingår i: Journal of High Energy Physics. - : Springer. - 1029-8479 .- 1126-6708. ; :11
-
Tidskriftsartikel (refereegranskat)
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| 26. |
- Aaltonen, T., et al.
(författare)
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Combination of Tevatron Searches for the Standard Model Higgs Boson in the W+W- Decay Mode
- 2010
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:6, s. 061802-
-
Tidskriftsartikel (refereegranskat)abstract
- We combine searches by the CDF and D0 Collaborations for a Higgs boson decaying to W+W-. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb(-1) of p (p) over bar collisions at root s = 1.96 TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard model Higgs boson in the mass range 162-166 GeV at the 95% C.L.
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| 27. |
- 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
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:7, s. 071804-
-
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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| 28. |
- 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
-
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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| 29. |
- Abazov, V. M., et al.
(författare)
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The upgraded DO detector
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 565:2, s. 463-537
-
Tidskriftsartikel (refereegranskat)abstract
- The DO experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid -argon calorimeters and central muon detector, remaining from Run 1, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DO.
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| 30. |
- Aaltonen, T., et al.
(författare)
-
Combination of CDF and D0 W-Boson mass measurements
- 2013
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052018-
-
Tidskriftsartikel (refereegranskat)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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| 31. |
- Aaltonen, T., et al.
(författare)
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Tevatron Run II combination of the effective leptonic electroweak mixing angle
- 2018
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:11
-
Tidskriftsartikel (refereegranskat)abstract
- Drell-Yan lepton pairs produced in the process p (p) over bar -> l(+)l(-) + X through an intermediate gamma*/Z boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter sin(2) theta(lept)(eff) using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to 9-10 fb(-1) of integrated luminosity. The combination of these measurements yields the most precise result from hadron colliders, sin(2)theta(lept)(eff) = 0.23148 +/- 0.00033. This result is consistent with, and approaches in precision, the best measurements from electron-positron colliders. The standard model inference of the on-shell electroweak mixing parameter sin(2) theta(W), or equivalently the W-boson mass M-W, using the ZFITTER software package yields sin(2) theta(W) = 0.22324 +/- 0.00033 or equivalently, M-W = 80.367 +/- 0.017 GeV/c(2).
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| 32. |
- Aaltonen, T., et al.
(författare)
-
Combination of measurements of the top-quark pair production cross section from the Tevatron Collider
- 2014
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 89:7
-
Tidskriftsartikel (refereegranskat)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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| 33. |
- Aaltonen, T., et al.
(författare)
-
Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron
- 2018
-
Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 120:4
-
Tidskriftsartikel (refereegranskat)abstract
- The CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of root s = 1.96 TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is A(FB)(t (t) over bar) = 0.128 +/- 0.025. The combined inclusive and differential asymmetries are consistent with recent standard model predictions.
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| 34. |
- Aaltonen, T., et al.
(författare)
-
Higgs boson studies at the Tevatron
- 2013
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052014-
-
Tidskriftsartikel (refereegranskat)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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| 35. |
- Aaltonen, T., et al.
(författare)
-
Observation of s-Channel Production of Single Top Quarks at the Tevatron
- 2014
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 112:23
-
Tidskriftsartikel (refereegranskat)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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| 36. |
- Aaltonen, T., et al.
(författare)
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Tevatron Combination of Single-Top-Quark Cross Sections and Determination of the Magnitude of the Cabibbo-Kobayashi-Maskawa Matrix Element V-tb
- 2015
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 115:15
-
Tidskriftsartikel (refereegranskat)abstract
- We present the final combination of CDF and D0 measurements of cross sections for single-top-quark production 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 t-channel cross section is measured to be sigma(t) = 2.25(-0.31)(+0.29) pb. We also present the combinations of the two-dimensional measurements of the s- vs t-channel cross section. In addition, we give the combination of the s + t channel cross section measurement resulting in sigma(s+t) = 3.30(-0.40)(+0.52) pb, without assuming the standard model value for the ratio sigma(s)/sigma(t). The resulting value of the magnitude of the top-to-bottom quark coupling is vertical bar V-tb vertical bar = 1.02(-0.05)(+0.06), corresponding to vertical bar V-tb vertical bar > 0.92 at the 95% C. L.
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| 37. |
- Aaltonen, T., et al.
(författare)
-
Tevatron Constraints on Models of the Higgs Boson with Exotic Spin and Parity Using Decays to Bottom-Antibottom Quark Pairs
- 2015
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 114:15
-
Tidskriftsartikel (refereegranskat)abstract
- Combined constraints from the CDF and D0 Collaborations on models of the Higgs boson with exotic spin J and parity P are presented and compared with results obtained assuming the standard model value J(P) = 0(+). Both collaborations analyzed approximately 10 fb(-1) of proton-antiproton collisions with a center-of-mass energy of 1.96 TeV collected at the Fermilab Tevatron. Two models predicting exotic Higgs bosons with J(P) = 0(-) and J(P) = 2(+) are tested. The kinematic properties of exotic Higgs boson production in association with a vector boson differ from those predicted for the standard model Higgs boson. Upper limits at the 95% credibility level on the production rates of the exotic Higgs bosons, expressed as fractions of the standard model Higgs boson production rate, are set at 0.36 for both the J(P) = 0(-) hypothesis and the J(P) = 2(+) hypothesis. If the production rate times the branching ratio to a bottom-antibottom pair is the same as that predicted for the standard model Higgs boson, then the exotic bosons are excluded with significances of 5.0 standard deviations and 4.9 standard deviations for the J(P) = 0(-) and J(P) = 2(+) hypotheses, respectively.
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| 38. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the isolated photon cross section in p(p)over-bar collisions at root s=1.96 TeV
- 2006
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 639:3-4, s. 151-158
-
Tidskriftsartikel (refereegranskat)abstract
- The cross section for the inclusive production of isolated photons has been measured in p (p) over bar collisions at root s = 1.96 TeV with the DO detector at the Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV and have pseudorapidity vertical bar n vertical bar < 0.9. The cross section is compared with the results from two next-to-leading order perturbative QCD calculations. The theoretical predictions agree with the measurement within uncertainties.
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| 39. |
- Abazov, V. M., et al.
(författare)
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Search for W ' boson production in the W ' -> t(b)over-bar decay channel
- 2006
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 641:6, s. 423-431
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the production of a new heavy gauge boson W' that decays to a top quark and a bottom quark. We have analyzed 230 pb(-1) of data collected with the DO detector at the Fermilab Tevatron collider at a center-of-mass energy of 1.96 TeV. No significant excess of events above the standard model expectation is found in any region of the final state invariant mass distribution. We set upper limits on the production cross section of W' bosons times branching ratio to top quarks at the 95% confidence level for several different W, boson masses. We exclude masses between 200 and 610 GeV for a W' boson with standard-model-like couplings, between 200 and 630 GeV for a W, boson with right-handed couplings that is allowed to decay to both leptons and quarks, and between 200 and 670 GeV for a W' boson with right-handed couplings that is only allowed to decay to quarks.
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| 40. |
- Abazov, V. M., et al.
(författare)
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Evidence for production of single top quarks and first direct measurement of vertical bar V-tb vertical bar
- 2007
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 98:18, s. 181802-
-
Tidskriftsartikel (refereegranskat)abstract
- The D0 Collaboration presents first evidence for the production of single top quarks at the Fermilab Tevatron < p(p)over bar > collider. Using a 0.9 fb(-1) dataset, we apply a multivariate analysis to separate signal from background and measure sigma(< p(p)over bar >-> tb+X,tqb+X)=4.9 +/- 1.4 pb. The probability to measure a cross section at this value or higher in the absence of a signal is 0.035%, corresponding to a 3.4 standard deviation significance. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa matrix element that describes the Wtb coupling and find 0.68 <= 1 at 95% C.L. within the standard model.
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| 41. |
- Abazov, V. M., et al.
(författare)
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Measurement of beta (t -> Wb)/beta(t -> Wq) at root s=1.96 TeV
- 2006
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 639:6, s. 616-622
-
Tidskriftsartikel (refereegranskat)abstract
- We present the measurement of R = B(t -> Wb)/B(t -> Wq) in pp collisions at root s = 1.96 TeV, using 230 pb(-1) of data collected by the DO experiment at the Fermilab Tevatron Collider. We fit simultaneously R and the number (N-tt) of selected top quark pairs (tt), to the number of identified b-quark jets in events with one electron or one muon, three or more jets, and high transverse energy imbalance. To improve sensitivity, kinematical properties of events with no identified b-quark jets are included in the fit. We measure R = 1.03(-0.17)(0.19) (stat + syst), in good agreement with the standard model. We set lower limits of R > 0.61 and vertical bar V-tb vertical bar > 0.78 at 95% confidence level.
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| 42. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the differential cross section for the production of an isolated photon with associated jet in p(p)over-bar collisions at root s=1.96 TeV
- 2008
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 666:5, s. 435-445
-
Tidskriftsartikel (refereegranskat)abstract
- The process p (p) over bar -> gamma + jet + X is studied using 1.0 fb(-1) of data collected by the DO detector at the Fermilab Tevatron p (p) over bar collider at a center-of-mass energy root s = 1.96 TeV. Photons are reconstructed in the central rapidity region vertical bar y(gamma)vertical bar < 1.0 with transverse momenta in the range 30 < p(T)(gamma) < 400 GeV while jets are reconstructed in either the central vertical bar y(jet)vertical bar < 0.8 or forward 1.5 < vertical bar y(jet)vertical bar < 2.5 rapidity intervals with P-T(jet) > 15 GeV. The differential cross section d(3 sigma)/dp(T)(gamma) dy(gamma) dy(jet) is measured as a function of p(T)(gamma) in four regions, differing by the relative orientations of the photon and the jet in rapidity. Ratios between the differential cross sections in each region are also presented. Next-to-leading order QCD predictions using different parameterizations of parton distribution functions and theoretical scale choices are compared to the data. The predictions do not simultaneously describe the measured normalization and p(T)(gamma) dependence of the cross section in the four measured regions.
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| 43. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the top quark mass in the dilepton channel
- 2007
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 655:1-2, s. 7-14
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the top quark mass in the dilepton channel based on approximately 370 pb(-1) of data collected by the DO experiment during Run R of the Fermilab Tevatron collider. We employ two different methods to extract the top quark mass. We show that both methods yield consistent results using ensemble tests of events generated with the DO Monte Carlo simulation. We combine the results from the two methods to obtain a top quark mass m(t) = 178.1 +/- 8.2 GeV. The statistical uncertainty is 6.7 GeV and the systematic uncertainty is 4.8 GeV.
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| 44. |
- Abazov, V. M., et al.
(författare)
-
Search for a heavy resonance decaying into a Z plus jet final state in p(p)over-bar collisions at root s=1.96 TeV using the D0 detector
- 2006
-
Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 74:1, s. 011104-
-
Tidskriftsartikel (refereegranskat)abstract
- We have searched for a heavy resonance decaying into a Z+jet final state in p (p) over bar collisions at a center of mass energy of 1.96 TeV at the Fermilab Tevatron collider using the D0 detector. No indication for such a resonance was found in a data sample corresponding to an integrated luminosity of 370 pb(-1). We set upper limits on the cross section times branching fraction for heavy resonance production at the 95% C.L. as a function of the resonance mass and width. The limits are interpreted within the framework of a specific model of excited quark production.
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| 45. |
- Abazov, V. M., et al.
(författare)
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Search for production of single top quarks via tcg and tug flavor-changing-neutral-current couplings
- 2007
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:19, s. 191802-
-
Tidskriftsartikel (refereegranskat)abstract
- We search for the production of single top quarks via flavor-changing-neutral-current couplings of a gluon to the top quark and a charm (c) or up (u) quark. We analyze 230 pb(-1) of lepton+jets data from p (p) over tilde collisions at a center of mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We observe no significant deviation from standard model predictions, and hence set upper limits on the anomalous coupling parameters kappa(c)(g)/Lambda and kappa(u)(g)/Lambda, where kappa(g) define the strength of tcg and tug couplings, and Lambda defines the scale of new physics. The limits at 95% C.L. are kappa(c)(g)/Lambda < 0.15 TeV-1 and kappa(u)(g)/Lambda < 0.037 TeV-1.
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| 46. |
- Abazov, V. M., et al.
(författare)
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Search for R-parity violating supersymmetry via the LL(E)over-bar couplings lambda(121), lambda(122) or lambda(133) in p(p)over-bar collisions at root s=1.96 TeV
- 2006
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 638:5-6, s. 441-449
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Tidskriftsartikel (refereegranskat)abstract
- A search for gaugino pair production with a trilepton signature in the framework of R-parity violating supersymmetry via the couplings; lambda(121), lambda(122), or lambda(133) is presented. The data, corresponding to an integrated luminosity of L approximate to 360 pb(-1), were collected from April 2002 to August 2004 with the D0 detector at the Fermilab Tevatron Collider, at a center-of-mass energy of root s = 1.96 TeV. This analysis considers final states with three charged leptons with the flavor combinations eel, mu mu l, and ee tau (l = e or mu). No evidence for supersymmetry is found and limits at the 95% confidence level are set on the gaugino pair production cross section and lower bounds on the masses of the lightest neutralino and chargino are derived in two supersymmetric models.
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| 47. |
- Abazov, V. M., et al.
(författare)
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Search for the lightest scalar top quark in events with two leptons in p(p)over-bar collisions at root s=1.96 TeV
- 2008
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 659:3, s. 500-508
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Tidskriftsartikel (refereegranskat)abstract
- Data collected by the DO detector at a p (p) over bar center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider have been used to search for pair production of the lightest supersymmetric partner of the top quark decaying into bl (nu) over tilde. The search is performed in the ll' = e mu and mu mu final states. No evidence for this process has been found in data samples of approximately 400 pb(-1). The domain in the [M((t) over tilde (1)), M((nu) over tilde)] plane excluded at the 95% C.L. is substantially extended by this search.
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| 48. |
- Abazov, V. M., et al.
(författare)
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A combined search for the standard model Higgs boson at root S=1.96 TeV
- 2008
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 663:1-2, s. 26-36
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Tidskriftsartikel (refereegranskat)abstract
- We present new results of the search for WH --> lvb (b) over bar production in p (p) over bar collisions at a center-of-mass energy of root S = 1.96 TeV, based on a dataset with integrated luminosity of 0.44 fb(-1). We combine these new results with previously published searches by the DO collaboration, for WH and ZH production analyzed in the E(T)b (b) over bar final state, for ZH (--> l(+)l(-)b (b) over bar) production, for WH (-->. WWW) production, and for H (--> W W) direct production. No signal-like excess is observed either in the W H analysis or in the combination of all D0 Higgs boson analyses. We set 95% C.L. (expected) upper limits on sigma(p (p) over bar --> WH) x B(H --> b (b) over bar) ranging from 1.6 (2.2) ph to 1.9 (3.3) pb for Higgs boson masses between 105 and 145 GeV, to be compared to the theoretical prediction of 0.13 pb for a Standard Model (SM) Higgs boson with mass in m(H) = 115 GeV. After combination with the other DO Higgs boson searches, we obtain for in H = 115 GeV an observed (expected) limit 8.5 (12.1) times higher than the SM predicted Higgs boson production cross section. For m(H) = 160 GeV, the corresponding observed (expected) ratio is 10.2 (9.0).
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| 49. |
- Abazov, V. M., et al.
(författare)
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Determination of the strong coupling constant from the inclusive jet cross section in pp collisions at s=1.96 TeV
- 2009
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Ingår i: PHYS REV D. - 1550-7998 .- 1550-2368. ; 80, s. 111107-
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Tidskriftsartikel (refereegranskat)abstract
- We determine the strong coupling constant alpha(s) and its energy dependence from the p(T) dependence of the inclusive jet cross section in pp collisions at s=1.96 TeV. The strong coupling constant is determined over the transverse momentum range 50 < p(T)< 145 GeV. Using perturbative QCD calculations to order O(alpha(3)(s)) combined with O(alpha(4)(s)) contributions from threshold corrections, we obtain alpha(s)(M-Z)=0.1161(-0.0048)(+0.0041). This is the most precise result obtained at a hadron-hadron collider.
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| 50. |
- Abazov, V. M., et al.
(författare)
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Evidence for production of single top quarks
- 2008
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; D:78, s. 012005-
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Forskningsöversikt (refereegranskat)abstract
- We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron p (p) over bar collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top-quark partner that is always produced from strong-coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top-quark production has been searched for in ever larger data sets. In this analysis, we select events from a 0.9 fb(-1) data set that have an electron or muon and missing transverse energy from the decay of a W boson from the top-quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W + jets and t (t) over bar events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix-element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top-quark production of sigma(p (p) over bar -> tb + X, tqb + X) = 4.7 +/- 1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top-quark production. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa quark mixing matrix element that describes the Wtb coupling and find vertical bar V(tb)f(1)(L)vertical bar = 1.31(-0.21)(+0.25), where f(1)(L) is a generic vector coupling. This model-independent measurement translates into 0.68 <= 1 at the 95% C.L. in the standard model.
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