| 1. |
- Abazov, V. M., et al.
(författare)
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Z(gamma) production and limits on anomalous ZZ(gamma) and Z(gamma gamma) couplings in p(p)over-bar collisions at root s 1.96 TeV
- 2012
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Ingår i: Physical Review D. - 1550-7998. ; 85:5, s. 052001
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of p (p) over bar -> Z gamma -> l(+)l(-)gamma (l = e, mu) production with a data sample corresponding to an integrated luminosity of 6.2 fb(-1) collected by the D0 detector at the Fermilab Tevatron p (p) over bar Collider. The results of the electron and muon channels are combined, and we measure the total production cross section and the differential cross section d(sigma)/dp(T)(gamma), where p(T)(gamma) is the momentum of the photon in the plane transverse to the beam line. The results obtained are consistent with the standard model predictions from next-to-leading order calculations. We use the transverse momentum spectrum of the photon to place limits on anomalous ZZ gamma and Z gamma gamma couplings.
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| 2. |
- Åsman, Barbro, 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. ; 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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| 3. |
- Åsman, Barbro, et al.
(författare)
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Measurement of the relative branching ratio of B-s(0) -> J/psi f(0)(980) to B-s(0) -> J/psi phi
- 2012
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Ingår i: Physical Review D. - 1550-7998. ; 85:1, s. 011103
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the relative branching fraction, R-f0/phi, of B-s(0) -> J/psi f(0)(980), with f(0)(980) -> pi(+)pi(-), to the process B-s(0) -> J/psi phi, with phi -> K+K-. The J/psi f(0)(980) final state corresponds to a CP-odd eigenstate of B-s(0) that could be of interest in future studies of CP violation. Using 8 fb(-1) of data recorded with the D0 detector at the Fermilab Tevatron Collider, we find R-f0/phi = 0.275 +/- 0.041(stat) +/- 0.061(syst).
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| 4. |
- Åsman, Barbro, et al.
(författare)
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Measurements of WW and WZ Production in W plus jets Final States in p(p)over-bar Collisions
- 2012
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Ingår i: Physical Review Letters. - 0031-9007. ; 108:18, s. 181803
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Tidskriftsartikel (refereegranskat)abstract
- We study WW and WZ production with lvqq (l = e, mu) final states using data collected by the D0 detector at the Fermilab Tevatron Collider corresponding to 4.3 fb(-1) of integrated luminosity from p (p) over bar collisions at root s = 1.96 TeV. Assuming the ratio between the production cross sections sigma(WW) and sigma(WZ) as predicted by the standard model, we measure the total WV (V = W, Z) cross section to be sigma(WV) = 19.6(-3.0)(+3.2) pb and reject the background-only hypothesis at a level of 7.9 standard deviations. We also use b-jet discrimination to separate the WZ component from the dominant WW component. Simultaneously fitting WW and WZ contributions, we measure sigma(WW) = 15.9(-3.2)(+3.7) pb and sigma(WZ) = 3.3(-3.3)(+4.1) pb, which is consistent with the standard model predictions.
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| 5. |
- Åsman, Barbro, et al.
(författare)
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Search for anomalous Wtb couplings in single top quark production in p(p)over-bar collisions at root s=1.96 TeV
- 2012
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Ingår i: Physics Letters B. - 0370-2693. ; 708:1-2, s. 21-26
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Tidskriftsartikel (refereegranskat)abstract
- We present new direct constraints on a general Wtb interaction using data corresponding to an integrated luminosity of 5.4 fb(-1) collected by the DO detector at the Tevatron p (p) over bar collider. The standard model provides a purely left-handed vector coupling at the Wtb vertex, while the most general, lowest dimension Lagrangian allows right-handed vector and left- or right-handed tensor couplings as well. We obtain precise limits on these anomalous couplings by comparing the data to the expectations from different assumptions on the Wtb coupling.
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| 6. |
- Åsman, Barbro, et al.
(författare)
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Search for Charged Massive Long-Lived Particles
- 2012
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Ingår i: Physical Review Letters. - 0031-9007. ; 108:12, s. 121802
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Tidskriftsartikel (refereegranskat)abstract
- We report on a search for charged massive long-lived particles (CMLLPs), based on 5.2 fb(-1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron p (p) over bar collider. We search for events in which one or more particles are reconstructed as muons but have speed and ionization energy loss (dE/dx) inconsistent with muons produced in beam collisions. CMLLPs are predicted in several theories of physics beyond the standard model. We exclude pair-produced long-lived gauginolike charginos below 267 GeV and Higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar top quarks with mass below 285 GeV.
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| 7. |
- 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. ; 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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| 8. |
- Abazov, V. M., et al.
(författare)
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Model indedpendent search for new phenomena in p(p)over-bar collisions at root s=1.96 TeV
- 2012
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Ingår i: Physical Review D. - 1550-7998. ; 85:9, s. 092015
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Tidskriftsartikel (refereegranskat)abstract
- We describe a model-independent search for physics beyond the standard model in lepton final states. We examine 117 final states using 1.1 fb(-1) of p (p) over bar collisions data at root s = 1.96 TeV collected with the D0 detector. We conclude that all observed discrepancies between data and model can be attributed to uncertainties in the standard model background modeling, and hence we do not see any evidence for physics beyond the standard model.
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| 9. |
- Abazov, V. M., et al.
(författare)
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Search for Higgs bosons of the minimal supersymmetric standard model in p(p)over-bar collisions at root s=1.96 TeV D0 Collaboration
- 2012
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Ingår i: Physics Letters B. - 0370-2693. ; 710:4-5, s. 569-577
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Tidskriftsartikel (refereegranskat)abstract
- We report results from searches for neutral Higgs bosons produced in p (p) over bar collisions recorded by the D0 experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral Higgs boson in the tau tau final state and in association with a b quark in the b tau tau and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are set for Higgs boson masses ranging from 90 to 300 GeV. We exclude tan beta > 20-30 for Higgs boson masses below 180 GeV. These are the most stringent constraints on MSSM Higgs boson production in p (p) over bar collisions.
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| 10. |
- Abazov, V. M., et al.
(författare)
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Search for pair production of the scalar top quark in muon plus tau final states D0 Collaboration
- 2012
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Ingår i: Physics Letters B. - 0370-2693. ; 710:4-5, s. 578-586
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Tidskriftsartikel (refereegranskat)abstract
- We present a search for the pair production of scalar top quarks ((t) over tilde (1)), the lightest supersymmetric partners of the top quarks, in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of 7.3 fb(-1) collected with the D0 experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a b quark, a charged lepton, and a scalar neutrino ((nu) over bar). We investigate final states arising from (t) over tilde (1)(t) over tilde (1) -> b (b) over bar mu tau(nu nu) over tilde and (t) over tilde (1)(t) over tilde (1) -> b (b) over bar tau tau(nu nu) over tilde. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the (m((t) over tilde1), m((nu) over tilde)) plane.
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