49 research outputs found

    利子の形成について(上)

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    The lifetime of the B0 s meson is measured in the decay channel B0 s → J=ψπþπ− with 880 ≤ Mπþπ− ≤ 1080 MeV=c2, which is mainly a CP-odd state and dominated by the f0ð980Þ resonance. In 10.4 fb−1 of data collected with the D0 detector in Run II of the Tevatron, the lifetime of the B0 s meson is measured to be τðB0 s Þ ¼ 1.70 0.14ðstatÞ 0.05ðsystÞ ps. Neglecting CP violation in B0 s=B¯ 0 s mixing, the measurement can be translated into the width of the heavy mass eigenstate of the B0 s , ΓH ¼ 0.59 0.05ðstatÞ 0.02ðsystÞ ps−1. D

    Measurement of the electron charge asymmetry in ppˉW+Xeν+X\boldsymbol{p\bar{p}\rightarrow W+X \rightarrow e\nu +X} decays in ppˉ\boldsymbol{p\bar{p}} collisions at s=1.96\boldsymbol{\sqrt{s}=1.96}~TeV

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    We present a measurement of the electron charge asymmetry in ppˉW+Xeν+Xp\bar{p}\rightarrow W+X \rightarrow e\nu +X events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7~fb1^{-1} of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date.We present a measurement of the electron charge asymmetry in pp¯→W+X→eν+X events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7  fb−1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date.We present a measurement of the electron charge asymmetry in ppˉW+Xeν+Xp\bar{p}\rightarrow W+X \rightarrow e\nu +X events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7~fb1^{-1} of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date

    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.We present a measurement of the distribution of the variable ϕη* 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  fb−1 at s=1.96  TeV. The data are corrected for detector effects and presented in bins of dimuon rapidity and mass. The variable ϕη* probes the same physical effects as the Z/γ* 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* distributions for dilepton masses away from the Z→ℓ+ℓ- boson mass peak. The data are compared to QCD predictions based on the resummation of multiple soft gluons.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

    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 yγ15|y^\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

    Precise measurement of the top quark mass in dilepton decays using optimized neutrino weighting

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    We measure the top quark mass in dilepton final states of top-antitop events in proton-antiproton collisions at sqrt(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 top-antitop to 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

    Measurement of spin correlation between top and antitop quarks produced in ppˉp\bar{p} collisions at s=1.96\sqrt{s} = 1.96 TeV

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    We present a measurement of the correlation between the spins of t and tbar quarks produced in proton-antiproton collisions at the Tevatron Collider at a center-of-mass energy of 1.96 TeV. We apply a matrix element technique to dilepton and single-lepton+jets final states in data accumulated with the D0 detector that correspond to an integrated luminosity of 9.7 fb1^{-1}. The measured value of the correlation coefficient in the off-diagonal basis, Ooff=0.89±0.22O_{off} = 0.89 \pm 0.22 (stat + syst), is in agreement with the standard model prediction, and represents evidence for a top-antitop quark spin correlation difference from zero at a level of 4.2 standard deviations.We present a measurement of the correlation between the spins of t and t¯ quarks produced in proton–antiproton collisions at the Tevatron Collider at a center-of-mass energy of 1.96 TeV. We apply a matrix element technique to dilepton and single-lepton+jets final states in data accumulated with the D0 detector that correspond to an integrated luminosity of 9.7 fb−1 . The measured value of the correlation coefficient in the off-diagonal basis, Ooff=0.89±0.22(stat+syst) , is in agreement with the standard model prediction, and represents evidence for a top–antitop quark spin correlation difference from zero at a level of 4.2 standard deviations.We present a measurement of the correlation between the spins of t and tbar quarks produced in proton-antiproton collisions at the Tevatron Collider at a center-of-mass energy of 1.96 TeV. We apply a matrix element technique to dilepton and single-lepton+jets final states in data accumulated with the D0 detector that correspond to an integrated luminosity of 9.7 fb1^{-1}. The measured value of the correlation coefficient in the off-diagonal basis, Ooff=0.89±0.22O_{off} = 0.89 \pm 0.22 (stat + syst), is in agreement with the standard model prediction, and represents evidence for a top-antitop quark spin correlation difference from zero at a level of 4.2 standard deviations
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