| 1. |
- Abazov, V. M., et al.
(author)
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Measurement of the t-channel single top quark production cross section
- 2010
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 682:4-5, s. 363-369
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Journal article (peer-reviewed)abstract
- The DO Collaboration reports direct evidence for electroweak production of single top quarks through the t-channel exchange of a virtual W boson. This is the first analysis to isolate an individual single top quark production channel. We select events containing an isolated electron or muon, missing transverse energy, and two, three or four jets from 2.3 fb(-1) of p (p) over bar collisions at the Fermilab Tevatron Collider. One or two of the jets are identified as containing a b hadron. We combine three multivariate techniques optimized for the t-channel process to measure the t- and s-channel cross sections simultaneously. We measure cross sections of 3.14(-0.80)(+0.94) pb for the t-channel and 1.05 +/- 0.81 pb for the s-channel. The measured t-channel result is found to have a significance of 4.8 standard deviations and is consistent with the standard model prediction.
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| 2. |
- Abazov, V. M., et al.
(author)
-
Search for single top quarks in the tau plus jets channel using 4.8 fb(-1) of p(p)over-bar collision data
- 2010
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 690:1, s. 5-14
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Journal article (peer-reviewed)abstract
- We present the first direct search for single top quark production using reconstructed tau leptons in the final state. The search is based on 4.8 fb(-1) of integrated luminosity collected in p (p) over bar collisions at root s= 1.96 TeV with the D0 detector at the Fermilab Tevatron Collider. We select events with a final state including an isolated tau lepton. missing transverse energy, two or three jets, one or two of them being identified as b quark jet. We use a multivariate technique to discriminate signal from background. The number of events observed in data in this final state is consistent with the signal plus background expectation. We set in the tau + jets channel an upper limit on the single top quark cross section of 7.3 pb at the 95% C.L. This measurement allows a gain of 4% in expected sensitivity for the observation of single top production when combining it with electron + jets and muon + jets channels already published by the DO Collaboration with 2.3 fb(-1) of data. We measure a combined cross section of 3.84(-0.83)(+0.89) pb, which is the most precise measurement to date.
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| 3. |
- Abazov, V. M., et al.
(author)
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Search for the Associated Production of a b Quark and a Neutral Supersymmetric Higgs Boson that Decays into τ Pairs
- 2010
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In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 104:15
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Journal article (peer-reviewed)abstract
- We report results from a search for production of a neutral Higgs boson in association with a b quark. We search for Higgs decays to tau pairs with one tau subsequently decaying to a muon and the other to hadrons. The data correspond to 2: 7 fb(-1) of p (p) over bar collisions recorded by the D0 detector at.. root s = 1.96 TeV. The data are found to be consistent with background predictions. The result allows us to exclude a significant region of parameter space of the minimal supersymmetric model.
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| 4. |
- Abazov, V. M., et al.
(author)
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Measurement of the ratios of the Z/gamma*+ >= n jet production cross sections to the total inclusive Z/gamma* cross section in p(p)over-bar collisions at root s=1.96 TeV
- 2008
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In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 658, s. 112-
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Journal article (peer-reviewed)abstract
- We present a study of events with Z bosons and associated jets produced at the Fermilab Tevatron collider in p p collisions at a center of mass energy of 1.96 TeV The data sample consists of nearly 14000 Z/gamma* -> e(+)e(-) candidates corresponding to an integrated luminosity of 0.4 fb(-1) collected with the D circle divide detector. Ratios of the Z/gamma*+ >= n jet cross sections to the total inclusive Z/gamma* cross section have been measured for n = 1-4 jets, and found to be in good agreement with a next-to-leading order QCD calculation and with a tree-level QCD prediction with parton shower simulation and hadronization.
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| 5. |
- Abazov, V. M., et al.
(author)
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Measurement of the t(t)over-bar production cross section in p(p)over-bar collisions at root s=1.96 TeV
- 2008
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:19:100, s. 192004-
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Journal article (peer-reviewed)abstract
- We measure the t (t) over bar production cross section in p (p) over bar collisions at root s = 1.96 TeV in the lepton + jets channel. Two complementary methods discriminate between signal and background: b tagging and a kinematic likelihood discriminant. Based on 0.9 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider, we measure sigma(t (t) over bar) = 7.62 +/- 0.85 pb, assuming the current world average m(t) = 172.6 GeV. We compare our cross section measurement with theory predictions to determine a value for the top-quark mass of 170 +/- 7 GeV.
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| 6. |
- Abazov, V. M., et al.
(author)
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Observation of the B-c meson in the exclusive decay B-c -> J/psi pi
- 2008
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 101:1, s. 012001-:101, s. 012001-
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Journal article (peer-reviewed)abstract
- A fully reconstructed B-c -> J/psi pi signal is observed with the D0 detector at the Fermilab Tevatron p (p) over bar collider using 1.3 fb(-1) of integrated luminosity. The signal consists of 54 +/- 12 candidates with a significance that exceeds 5 standard deviations, and confirms earlier observations of this decay. The measured mass of the B-c meson is 6300 +/- 14(stat)+/- 5(syst) MeV/c(2).
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| 7. |
- Abazov, V. M., et al.
(author)
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Search for W ' boson resonances decaying to a top quark and a bottom quark
- 2008
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:21, s. 211803-:100, s. 211803-
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Journal article (peer-reviewed)abstract
- We search for the production of a heavy W ' gauge boson that decays to third generation quarks in 0: 9 fb(-1) of p (p) over bar collisions at root s = 1: 96 TeV, collected with the D0 detector at the Fermilab Tevatron collider. We find no significant excess in the final-state invariant mass distribution and set upper limits on the production cross section times branching fraction. For a left-handed W ' boson with SM couplings, we set a lower mass limit of 731 GeV. For right-handed W ' bosons, we set lower mass limits of 739 GeV if the W ' boson decays to both leptons and quarks and 768 GeV if the W ' boson decays only to quarks. We also set limits on the coupling of the W ' boson to fermions as a function of its mass.
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| 8. |
- Abazov, V. M., et al.
(author)
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Search for W ' bosons decaying to an electron and a neutrino with the D0 detector
- 2008
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:3, s. 031804-:100, s. 031804-
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Journal article (peer-reviewed)abstract
- This Letter describes the search for a new heavy charged gauge boson W-' decaying into an electron and a neutrino. The data were collected with the D0 detector at the Fermilab Tevatron p (p) over bar Collider at root s=1.96 TeV, and correspond to an integrated luminosity of about 1 fb(-1). Lacking any significant excess in the data in comparison with known processes, an upper limit is set on sigma(')(W)xB(W-'-> e nu), and a W-' boson with mass below 1.00 TeV can be excluded at the 95% C.L., assuming standard-model-like couplings to fermions. This result significantly improves upon previous limits and is the most stringent to date.
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| 9. |
- Abazov, V. M., et al.
(author)
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Search for ZZ and z gamma* production in p(p)over-bar collisions at root s=1.96 TeV and limits on anomalous ZZZ and ZZ gamma* couplings
- 2008
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:13, s. 131801-:100, s. 131801-
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Journal article (peer-reviewed)abstract
- We present a study of mu mu mu mu, eeee, and mu mu ee events using 1 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron p (p) over bar Collider at root s = 1.96 TeV. Requiring the lepton pair masses to be greater than 30 GeV, we observe one event, consistent with the expected background of 0.13 +/- 0.03 events and with the predicted standard model ZZ and Z gamma(*) production of 1.71 +/- 0.15 events. We set an upper limit on the ZZ and Z gamma(*) cross section of 4.4 pb at the 95% C.L. We also derive limits on anomalous neutral trilinear ZZZ and ZZ gamma(*) gauge couplings. The one-parameter 95% C.L. coupling limits with a form-factor scale Lambda = 1.2 TeV are -0.28 < f(40)(Z)< 0.28, -0.31 < f(50)(Z)< 0.29, -0.26 < f(40)(gamma)< 0.26, and -0.30 < f(50)(gamma)< 0.28.
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| 10. |
- Aad, G., et al.
(author)
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Commissioning of the ATLAS Muon Spectrometer with cosmic rays
- 2010
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:3, s. 875-916
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Journal article (peer-reviewed)abstract
- The ATLAS detector at the Large Hadron Collider has collected several hundred million cosmic ray events during 2008 and 2009. These data were used to commission the Muon Spectrometer and to study the performance of the trigger and tracking chambers, their alignment, the detector control system, the data acquisition and the analysis programs. We present the performance in the relevant parameters that determine the quality of the muon measurement. We discuss the single element efficiency, resolution and noise rates, the calibration method of the detector response and of the alignment system, the track reconstruction efficiency and the momentum measurement. The results show that the detector is close to the design performance and that the Muon Spectrometer is ready to detect muons produced in high energy proton-proton collisions.
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