926 research outputs found

    Measurement of the ratio of inclusive cross sections σ(ppˉZ+2 bjets)/σ(ppˉZ+2 jets)\sigma (p\bar{p} \rightarrow Z+2~b \text{jets}) / \sigma (p\bar{p} \rightarrow Z+ \text{2 jets}) in ppˉp\bar{p} collisions at s=1.96\sqrt s=1.96 TeV

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    We measure the ratio of cross sections, σ(ppˉZ+2 b jets)\sigma(p\bar{p}\rightarrow Z+2~b~\text{jets})/σ(ppˉZ+2 jets)\sigma(p\bar{p}\rightarrow Z+\text{2 jets}), for associated production of a ZZ boson with at least two jets with transverse momentum pTjet>20p_T^{\rm jet} > 20 GeV and pseudorapidity ηjet<2.5|\eta^{\rm jet}| < 2.5. This measurement uses data corresponding to an integrated luminosity of 9.7 fb1^{-1} collected by the \DO experiment in Run II of Fermilab's Tevatron \ppbar Collider at a center-of-mass energy of 1.96 TeV. The measured integrated ratio of 0.0236\pm0.0032\left(\mbox{stat}\right)\pm0.0035\left(\mbox{syst}\right) is in agreement with predictions from next-to-leading-order perturbative QCD and the Monte Carlo event generators {\sc pythia} and {\sc alpgen}

    Precision measurement of the top-quark mass in lepton+jets final states

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    We measure the mass of the top quark in lepton++jets final states using the full sample of ppˉp\bar{p} collision data collected by the D0 experiment in Run II of the Fermilab Tevatron Collider at s=1.96\sqrt s=1.96 TeV, corresponding to 9.7fb19.7 {\rm fb}^{-1} of integrated luminosity. We use a matrix element technique that calculates the probabilities for each event to result from ttˉt\bar t production or background. The overall jet energy scale is constrained in situ by the mass of the WW boson. We measure mt=174.98±0.76m_t=174.98\pm0.76 GeV. This constitutes the most precise single measurement of the top-quark mass.Comment: submitted to Phys. Rev. D, 40 pages, detailed documentation of Phys. Rev. Lett. 113, 032002 (2014) [arXiv:1405.1756

    Improved bb quark jet identification at the D0 experiment

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    The ability to identify jets which originated from bb quarks is an important tool of the physics program of the D0 experiment at the Fermilab Tevatron ppˉp\bar{p} collider. This article describes a new algorithm designed to select jets originating from bb quarks while suppressing the contamination caused by jets from other quark flavors and gluons. Additionally, a new technique, the SystemN method, for determining the misidentification rate directly from data is presented.Comment: Submitted to Nucl. Instrum. Methods Phys. Res.

    Measurement of the differential γ+2 b\gamma+2~b-jet cross section and the ratio σ\sigma(γ+2 b\gamma+2~b-jets)/σ\sigma(γ+b\gamma+b-jet) in ppˉp\bar{p} collisions at s\sqrt{s}=1.96 TeV

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    We present the first measurements of the differential cross section dσ/dpTγd\sigma/dp_{T}^{\gamma} for the production of an isolated photon in association with at least two bb-quark jets. The measurements consider photons with rapidities yγ<1.0|y^\gamma| < 1.0 and transverse momenta 30<pTγ1530 < p_{T}^{\gamma} 15 GeV and yjet<1.5| y^{jet}| < 1.5. The ratio of differential production cross sections for γ+2 b\gamma+2~b-jets to γ+b\gamma+b-jet as a function of pTγp_{T}^{\gamma} is also presented. The results are based on the proton-antiproton collision data at s=\sqrt{s}=1.96~\TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next-to-leading order perturbative QCD calculations as well as predictions based on the kTk_{T}-factorization approach and those from the SHERPA and PYTHIA Monte Carlo event generators.Comment: 10 pages, 8 figures, Submitted to Phys. Lett.

    Measurement of the ϕη\phi^*_\eta distribution of muon pairs with masses between 30 and 500 GeV in 10.4 fb1^{-1} of ppˉp\bar{p} collisions

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    We present a measurement of the distribution of the variable ϕη\phi^*_\eta for muon pairs with masses between 30 and 500 GeV, using the complete Run II data set collected by the D0 detector at the Fermilab Tevatron proton-antiproton collider. This corresponds to an integrated luminosity of 10.4 fb1^{-1} at s\sqrt{s} = 1.96 TeV. The data are corrected for detector effects and presented in bins of dimuon rapidity and mass. The variable ϕη\phi^*_\eta probes the same physical effects as the Z/γZ/\gamma^* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. These are the first measurements at any collider of the ϕη\phi^*_\eta distributions for dilepton masses away from the Z+Z\rightarrow \ell^+\ell^- boson mass peak. The data are compared to QCD predictions based on the resummation of multiple soft gluons.Comment: Accepted for publication in Phys.Rev.
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