1,722,158 research outputs found
Precise measurement of the top quark mass in dilepton decays using optimized neutrino weighting
No full textWe measure the top quark mass in dilepton final states of t¯t events in p¯p collisions at √ s = 1.96 TeV, using data corresponding to an integrated luminosity of 9.7 fb−1 at the Fermilab Tevatron Collider. The analysis features a comprehensive optimization of the neutrino weighting method to minimize the statistical uncertainties. We also improve the calibration of jet energies using the calibration determined in t¯t →lepton + jets events, which reduces the otherwise limiting systematic uncertainty from the jet energy scale. The measured top quark mass is mt = 173.32 ±1.36(stat) ±0.85(syst) GeV
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New technologies in the D0 central tracker upgrade
Full text linkThe D0 collaboration has undertaken an aggressive upgrade of its central tracking system. The existing tracker will be completely removed and replaced by a two Tesla superconducting solenoidal magnet, an 837 000 channel silicon vertex system, and 80 000 channel scintillating fiber tracker, followed by a 7 680 channel central preshower detector and a 16 000 channel forward preshower detector. In this paper the author discusses all of the subsystems of the D0 central tracker upgrade, but will emphasize those aspects which involve new technology: radiation hard scintillating fiber, VLPC`s and extruded scintillating strips
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Search for the top quark using multivariate analysis techniques
No full textThe D0 collaboration is developing top search strategies using multivariate analysis techniques. We report here on applications of the H-matrix method to the e{mu} channel and neural networks to the e+jets channel
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A measurement of the ratio of W + 1 jet to W + 0 jets cross sections and comparisons to QCD
Full text linkA preliminary measurement of the ratio, R{sup 10}, of the production cross sections for W + 1 Jet and W + 0 Jets processes at {radical}s = 1,800 GeV by the D0 Collaboration is presented. A comparison of this ratio is made to next-to-leading order calculations and the implications of these comparisons, especially for the extraction of a value for the strong coupling constant {alpha}{sub s}(M{sub W}{sup 2}), are discussed
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Top quark physics at the D0 experiment
No full textIn this paper I present the latest results on top quark physics from the D0 collaboration since the discovery of the top quark in March 1995. I summarize the discovery results, discuss progress since the discovery, and show how we can measure the top quark mass using three separate techniques. The measurements were made at the Fermilab Tevatron, a p{bar p} collider with {radical}s = TeV, using {approximately}50 pb{sup {minus}1} data collected from 1992 to early 1995
Measurement of hard double-parton interactions in W(→ℓν) + 2-jet events at √<span style="text-decoration:overline">s</span>=7 TeV with the ATLAS detector
Full text linkThe production of W bosons in association with two jets in proton–proton collisions at a centre-of-mass energy of √<span style="text-decoration:overline">s</span>=7 TeV has been analysed for the presence of double-parton interactions using data corresponding to an integrated luminosity of 36 pb−1, collected with the ATLAS detector at the Large Hadron Collider. The fraction of events arising from double-parton interactions, f(D)DP, has been measured through the pT balance between the two jets and amounts to f(D)DP = 0.08 ± 0.01 (stat.) ± 0.02 (sys.) for jets with transverse momentum pT > 20 GeV and rapidity |y| < 2.8. This corresponds to a measurement of the effective area parameter for hard double-parton interactions of σeff = 15 ± 3 (stat.) +5−3 (sys.) mb
Study of the {X}^{\ifmmode\pm\else\textpm\fi{}}(5568) state with semileptonic decays of the meson
No full textWe present a study of the X±(5568) using semileptonic decays of the B0s meson using the full run II integrated luminosity of 10.4 fb−1 in proton-antiproton collisions at a center of mass energy of 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. We report evidence for a narrow structure, X±(5568), in the decay sequence X±(5568)→B0sπ± where B0s→μ∓D±sX, D±s→ϕπ± which is consistent with the previous measurement by the D0 Collaboration in the hadronic decay mode, X±(5568)→B0sπ± where B0s→J/ψϕ. The mass and width of this state are measured using a combined fit of the hadronic and semileptonic data, yielding m=5566.9+3.2−3.1(stat)+0.6−1.2(syst) MeV/c2, Γ=18.6+7.9−6.1(stat)+3.5−3.8(syst) MeV/c2 with a significance of 6.7σ
Search for excited electrons and muons in √s=8 TeV proton–proton collisions with the ATLAS detector
Full text linkThe ATLAS detector at the Large Hadron Collider is used to search for excited electrons and excited muons in the channel pp → ℓℓ* → ℓℓγ, assuming that excited leptons are produced via contact interactions. The analysis is based on 13 fb[superscript −1] of pp collisions at a centre-of-mass energy of 8 TeV. No evidence for excited leptons is found, and a limit is set at the 95% credibility level on the cross section times branching ratio as a function of the excited-lepton mass m[subscript ℓ*]. For m[subscript ℓ*] ≥ 0.8 TeV, the respective upper limits on σB(ℓ* → ℓγ) are 0.75 and 0.90 fb for the e* and μ* searches. Limits on σB are converted into lower bounds on the compositeness scale Λ. In the special case where Λ = m[subscript ℓ*], excited-electron and excited-muon masses below 2.2 TeV are excluded.United States. Dept. of EnergyNational Science Foundation (U.S.)Brookhaven National Laborator
Measurement of the W +b-jet and W +c-jet differential production cross sections in p¯p collisions at √s = 1.96 TeV
No full textWe present a measurement of the cross sections for the associated production of a W boson with at least one heavy quark jet, b or c , in proton–antiproton collisions. Data corresponding to an integrated luminosity of 8.7 fb−18.7 fb−1 recorded with the D0 detector at the Fermilab Tevatron View the MathML sourcepp¯ Collider at View the MathML sources=1.96 TeV are used to measure the cross sections differentially as a function of the jet transverse momenta in the range 20 to 150 GeV. These results are compared to calculations of perturbative QCD theory as well as predictions from Monte Carlo generators
Measurement of the ratio of three-jet to two-jet cross sections in p¯p collisions at √ s = 1.96 TeV
No full textWe present a measurement of the ratio of multijet cross sections in p¯p collisions at √ s = 1.96 TeV at the Fermilab Tevatron Collider. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb−1 collected with the D0 detector. The ratio of the inclusive three-jet to two-jet cross sections, R3/2, has been measured as a function of the jet transverse momenta. The data are compared to QCD predictions in different approximations. Popular tunes of the pythia event generator do not agree with the data, while sherpa provides a reasonable description of the data. A perturbative QCD prediction in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects, gives a good description of the data
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