| 31. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the production fraction times branching fraction f(b -> Lambda(b)) . B(Lambda(b) -> J/psi Lambda)
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:3, s. 031102-
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Tidskriftsartikel (refereegranskat)abstract
- The Lambda(b)(udb) baryon is observed in the decay Lambda(b) -> J/psi Lambda using 6.1fb(-1) of p (p) over bar collisions collected with the D0 detector at root s = 1/96 TeV. The production fraction multiplied by the branching fraction for this decay relative to that for the decay B(0) -> J/psi K(s)(0) is measured to be 0.345 +/- 0.034(stat) +/- 0.033(syst) +/- 0.003(PDG). Using the world average value of f(b -> B(0)) . B(B(0) -> J/psi K(s)(0) = (1.74 +/- 0.08) x 10(-5), we obtain f(b -> Lambda(b)) . B(Lambda(b) -> J/psi Lambda) = (6.01 +/- 0.60(stat) +/- 0.58(syst) +/- 0.28(PDG)) x 10(-5). This measurement represents an improvement in precision by about a factor of 3 with respect to the current world average.
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| 32. |
- Abazov, V. M., et al.
(författare)
-
Measurement of the ratio of inclusive cross sections sigma(p(p)over-bar -> Z plus b-quark jet)/sigma(p(p)over-bar -> Z plus jet) at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 83:3, s. 031105-
-
Tidskriftsartikel (refereegranskat)abstract
- The ratio of the cross section for p (p) over bar interactions producing a Z boson and at least one b-quark jet to the inclusive Z + jet cross section is measured using 4.2 fb(-1) of p (p) over bar collisions collected with the D0 detector at the Fermilab Tevatron collider at root s = 1.96 TeV. The Z -> l(+) l- candidate events with at least one b jet are discriminated from Z + charm and light jet(s) events by a novel technique that exploits the properties of the tracks associated to the jet. The measured ratio is 0: 0193 +/- 0: 0027 for events having a jet with transverse momentum p(T) > 20 GeV and pseudorapidity vertical bar eta vertical bar <= 2.5, which is the most precise to date and is consistent with theoretical predictions.
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| 33. |
- Abazov, V. M., et al.
(författare)
-
Measurements of inclusive W plus jets production rates as a function of jet transverse momentum in p(p)over-bar collisions root s=1.96 TeV
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 705:3, s. 200-207
-
Tidskriftsartikel (refereegranskat)abstract
- This Letter describes measurements of inclusive W (-> ev) + n jet cross sections (n = 1-4), presented as total inclusive cross sections and differentially in the nth jet transverse momentum. The measurements are made using data corresponding to an integrated luminosity of 4.2 fb(-1) collected by the DO detector at the Fermilab Tevatron Collider, and achieve considerably smaller uncertainties on W + jets production cross sections than previous measurements. The measurements are compared to next-to-leading order perturbative QCD (pQCD) calculations in the n = 1-3 jet multiplicity bins and to leading order pQCD calculations in the 4-jet bin. The measurements are generally in agreement with pQCD calculations, although certain regions of phase space are identified where these predictions could better match the data.
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| 34. |
- Abazov, V. M., et al.
(författare)
-
Precision Measurement of the Ratio B(t -> Wb)/B(t -> Wq) and Extraction of V(tb)
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:12, s. 121802-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the ratio of top quark branching fractions R = B(t -> Wb)/B(t -> Wq), where q can be a d, s, or b quark, in the lepton + jets and dilepton t (t) over bar final states. The measurement uses data from 5: 4 fb(-1) of p (p) over bar collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure R = 0.90 +/- 0.04, and we extract the Cabibbo-Kobayashi-Maskawa (CKM) matrix element vertical bar V(tb)vertical bar as vertical bar V(tb)vertical bar = 0.95 +/- 0.02, assuming unitarity of the 3 x 3 CKM matrix.
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| 35. |
- Abazov, V. M., et al.
(författare)
-
Search for a Fermiophobic and Standard Model Higgs Boson in Diphoton Final States
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:15, s. 151801-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the standard model Higgs boson and a fermiophobic Higgs boson in the diphoton final states based on 8.2 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No excess of data above background predictions is observed and upper limits at the 95% C.L. on the cross section multiplied by the branching fraction are set which are the most restrictive to date. A fermiophobic Higgs boson with a mass below 112.9 GeV is excluded at the 95% C.L.
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| 36. |
- Abazov, V. M., et al.
(författare)
-
Search for a Fourth Generation t ' Quark in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:8, s. 082001-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for pair production of a fourth generation t' quark and its antiparticle, followed by their decays to a W boson and a jet, based on an integrated luminosity of 5: 3 fb(-1) of proton-antiproton collisions at root s = 1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the t'(t) over bar' production cross section that exclude at the 95% C. L. a t' quark that decays exclusively to W + jet with a mass below 285 GeV. We observe a small excess in the mu + jets channel which reduces the mass range excluded compared to the expected limit of 320 GeV in the absence of a signal.
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| 37. |
- Abazov, V. M., et al.
(författare)
-
Search for associated Higgs boson production using like charge dilepton events in p(p)over-bar collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84, s. 092002-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for associated Higgs boson production in the process p (p) over bar -> W/ZH -> l(+/-)l'(+/-) + X in ee, e mu, and mu mu final states. The search is based on data collected by the D0 experiment at the Fermilab Tevatron Collider at root s = 1.96 TeV corresponding to 5.3 fb(-1) of integrated luminosity. We require two isolated leptons (electrons or muons) with the same electric charge and additional kinematic requirements. No significant excess above background is observed, and we set 95% C. L. observed (expected) upper limits on ratio of the production cross section to the standard model prediction of 6.4 (7.3) for a Higgs boson mass of 165 GeV and 13.5 (19.8) for a mass of 115 GeV.
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| 38. |
- Abazov, V. M., et al.
(författare)
-
Search for first generation leptoquark pair production in the electron plus missing energy plus jets final state
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:7, s. 071104-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for the pair production of first generation scalar leptoquarks (LQ) in data corresponding to an integrated luminosity of 5.4 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in p (p) over bar collisions at root s = 1.96 TeV. In the channel LQLQ -> eqv(e)q', where q, q' are u or d quarks, no significant excess of data over background is observed, and we set a 95% C. L. lower limit of 326 GeV on the LQ mass, assuming equal probabilities of LQ decays to eq and v(e)q'.
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| 39. |
- Abazov, V. M., et al.
(författare)
-
Search for flavor changing neutral currents in decays of top quarks
- 2011
-
Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 701:3, s. 313-320
-
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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| 40. |
- Abazov, V. M., et al.
(författare)
-
Search for Neutral Minimal Supersymmetric Standard Model Higgs Bosons Decaying to Tau Pairs Produced in Association with b Quarks in p(p)over-bar Collisions at root s=1.96 TeV
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:12, s. 121801-
-
Tidskriftsartikel (refereegranskat)abstract
- We report results from a search for neutral Higgs bosons produced in association with b quarks using data recorded by the D0 experiment at the Fermilab Tevatron Collider and corresponding to an integrated luminosity of 7.3 fb(-1). This production mode can be enhanced in several extensions of the standard model (SM) such as in its minimal supersymmetric extension (MSSM) at high tan beta. We search for Higgs bosons decaying to tau pairs with one tau decaying to a muon and neutrinos and the other to hadrons. The data are found to be consistent with SM expectations, and we set upper limits on the cross section times branching ratio in the Higgs boson mass range from 90 to 320 GeV/c(2). We interpret our result in the MSSM parameter space, excluding tan beta values down to 25 for Higgs boson masses below 170 GeV/c(2).
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