We have searched for second generation leptoquark (LQ) pairs in the \mu\mu+jets channel using 94+-5 pb^{-1} of pbar-p collider data collected by the D0 experiment at the Fermilab Tevatron during 1993-1996. No evidence for a signal is observed. These results are combined with those from the \mu\nu+jets and \nu\nu+jets channels to obtain 95% confidence level (C.L.) upper limits on the LQ pair production cross section as a function of mass and $beta, the branching fraction of a LQ decay into a charged lepton and a quark. Lower limits of 200(180) GeV/c^2 for \beta=1(1/2) are set at the 95% C.L. on the mass of scalar LQ. Mass limits are also set on vector leptoquarks as a function of \beta.
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This Letter describes a measurement of the muon cross section originating from b quark decay in the forward rapidity range 2.4 < y(mu) < 3.2 in pbarp collisions at sqrt(s) = 1.8 TeV. The data used in this analysis were collected by the D0 experiment at the Fermilab Tevatron. We find that NLO QCD calculations underestimate b quark production by a factor of four in the forward rapidity region. A cross section measurement using muon+jet data has been included in this version of the paper.
The forward muon cross section (per unit rapidity).
The cross section for muons originating from b-quark decay.
Integrated cross sections for muons originating from b-quark decay. The statistical and systematic errors are added in quadrature.
We present measurements of the b-bbar production cross section and angular correlations using the D0 detector at the Fermilab Tevatron p-pbar Collider operating at sqrt(s) = 1.8 TeV. The b quark production cross section for |y(b)|<1.0 and p_T(b)>6 GeV/c is extracted from single muon and dimuon data samples. The results agree in shape with the next-to-leading order QCD calculation of heavy flavor production but are greater than the central values of these predictions. The angular correlations between b and bbar quarks, measured from the azimuthal opening angle between their decay muons, also agree in shape with the next-to-leading order QCD prediction.
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The errors are combinations of statistical and systematic uncertainties.
The distribution of MU+ MU- azimuthal angle difference.
This paper presents the first measurement of the inclusive J/Psi production cross section in the forward pseudorapidity region 2.5<|eta|<3.7 in ppbar collisions at sqrt(s)=1.8TeV. The results are based on 9.8 pb-1 of data collected using the D0 detector at the Fermilab Tevatron Collider. The inclusive J/Psi cross section for transverse momenta between 1 and 16 GeV/c is compared with theoretical models of charmonium production.
Only statistical errors are shown. Cross section tines branching ratio.
Measurements are presented of the inclusive distributions of theJ/Ψ meson produced by muons of energy 200 GeV from an ammonia target. The gluon distribution of the nucleon has been derived from the data in the range 0.04<x<0.36 using a technique based on the colour singlet model. An arbitrary normalisation factor is required to obtain a reasonable integral of the gluon distribution. Some comments are made on the use ofJ/Ψ productionby virtual photons to extract the gluon distribution at HERA.
Data are normalized to total cross section of 36 nb (not corrected for coherence).
Data are normalized to total cross section of 36 nb (not corrected for coherence).
Data are normalized to total cross section of 36 nb (not corrected for coherence).
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Final data measured with the EMC forward spectrometer are presented on the production of forward charged hadrons in μp and μd scattering at incident beam energies between 100 and 280 GeV. The large statistic of 373 000 events allows a study of the semi-inclusive hadron production as a function ofz,pT2 and 〈pT2〉 in smallQ2,xBj andW bins. Charge multiplicity ratios and differences as a function ofz andxBj are given forp, d andn-targets. From the differences of charge multiplicities the ratio of the valence quark distributions of the protondv(x)/uv(x) is determined for the first time in charged lepton scattering. The Gronau et al. sum rule is tested, the measured sum being 0.31±0.06 stat. ±0.05 syst., compared with the theoretical expectation of 2/7≈0.286. The measured sum corresponds to an absolute value of the ratio of thed andu quark charge of 0.44±0.10 stat.±0.08 syst.
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The spin asymmetry in deep inelastic scattering of longitudinally polarised muons by longitudinally polarised protons has been measured in the range 0.01<×<0.7. The spin dependent structure function g 1 ( x ) for the proton has been determined and, combining the data with earlier SLAC measurements, its integral over x found to be 0.126±0.010(stat.)±0.015(syst.), in disagreement with the Ellis-Jaffe sum rule. Assuming the validity of the Biorken sum rule, this result implies a significant negative value for the integral of g 1 for the neutron. These integrals lead to the conclusion, in the naïve quark parton model, that the total quark spin constitutes a rather small fraction of the spin of the nucleon. Results are also presented on the asymmetries in inclusive hadron production which are consistent with the above picture.
THE MEAN Q**2 FOR EACH OF THE 10 VALUES OF X BELOW ARE 3.5,4.5,6.0, 8.010.3,12.9,15.2,18.0,22.5,29.5.
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The inclusive yield of photons has been measured from deep inelastic interactions of 200 GeV muons on hydrogen. After subtracting the contributions from hadron electromagnetic decays and Bethe-Heitler muon bremsstrahlung, residual photons are observed at low p T and low z at a mean level of 0.15±0.06 per interaction. The quark Compton scattering process is unable to explain the data, thus indicating an anomalous photon production.
Z distribution of anomalous direct photons.
PT distribution of anomalous direct photons.
Data are presented on exclusive ρ0 and ϕ production in deep inelastic muon scattering from a target consisting mainly of nitrogen. The ratio of the total cross sections for ρ0 and ϕ production is found to be 9∶(1.6±0.4) at 〈Q2〉=7.5 GeV2, consistent with theSU(3) prediction of 9∶2. Thet dependence for exclusive ρ0 production is found to become shallover asQ2 increases and, for largeQ2, thet dependence is typical of that for a hard scattering process. Furthermore, the ratio of the cross sections for coherent: incoherent production from nitrogen is found to decrease rapidly withQ2. Such behaviour indicates that even for exclusive vector meson production the virtual photon behaves predominantly as an electromagnetic probe.
No description provided.
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