| 221. |
- 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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| 222. |
- Abazov, V. M., et al.
(författare)
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Measurement of the Lambda(0)(b) lifetime in the exclusive decay Lambda(0)(b) -> J/psi Lambda(0) in p(p)over-bar collisions at root s=1.96 TeV
- 2012
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:11, s. 112003-
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Tidskriftsartikel (refereegranskat)abstract
- We measure the Lambda(0)(b) lifetime in the fully reconstructed decay Lambda(0)(b) -> J/psi Lambda(0) using 10.4 fb(-1) of p (p) over bar collisions collected with the D0 detector at root s = 1.96 TeV. The lifetime of the topologically similar decay channel B-0 -> J/psi K-S(0) is also measured. We obtain tau(Lambda(0)(b)) = 1.303 +/- 0.075(stat) +/- 0.035(syst) ps and tau(B-0) = 1.508 +/- 0.025(stat) +/- 0.043(syst) ps. Using these measurements, we determine the lifetime ratio of tau(Lambda(0)(b))/tau(B-0) = 0.864 +/- 0.052(stat) +/- 0.033(syst).
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| 223. |
- 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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| 224. |
- Abazov, V. M., 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 .- 1550-2368. ; 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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| 225. |
- Abazov, V. M., 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 .- 1079-7114. ; 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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| 226. |
- Abazov, V. M., et al.
(författare)
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Observation of a narrow mass state decaying into Y(1S)+gamma in p(p)over-bar collisions at root s=1.96 TeV
- 2012
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 86:3, s. 031103-
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Tidskriftsartikel (refereegranskat)abstract
- Using data corresponding to an integrated luminosity of 1.3 fb(-1), we observe a narrow mass state decaying into Gamma(1S) + gamma, where the Gamma(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551 +/- 0.014(stat) +/- 0.017(syst) GeV/c(2), which is consistent with that of the state recently observed by the ATLAS Collaboration.
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| 227. |
- Abazov, V. M., et al.
(författare)
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Search for a narrow t(t)over-bar resonance in p(p)over-bar collisions at root s=1.96 TeV
- 2012
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 85:5
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Tidskriftsartikel (refereegranskat)abstract
- We report a search for a narrow t (t) over bar resonance that decays into a lepton + jets final state 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 production cross section of such a resonance multiplied by its branching fraction to t (t) over bar. We exclude a leptophobic topcolor Z' at the 95% confidence level for masses below 835 GeV (940 GeV) if its width is 1.2% (3%) of its mass. We also exclude color octet vector bosons (colorons) with masses below 775 GeV.
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| 228. |
- Abazov, V. M., 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. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 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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| 229. |
- Abazov, V. M., 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 .- 1079-7114. ; 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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| 230. |
- 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
-
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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