[en] We report on a search for second generation scalar leptoquarks with the D0 detector at the Fermilab Tevatron ppbar collider at √s=1.8TeV. This search is based on 12.7pb^-1 of data. Second generation leptoquarks are assumed to be produced in pairs and to decay into a muon and quark with branching ratio β or into a neutrino and quark with branching ratio 1-β. We obtain cross section times branching ratio limits as a function of leptoquark mass and set lower limits on the leptoquark mass at the 95% confidence level. copyright 1995 The American Physical Society

[en] We report on a search for first generation leptoquarks with the DO detector at the Fermilab Tevatron p bar p collider at √s =1.8 TeV. This search is based on 15 pb^-1 of data. Leptoquarks are assumed to be produced in pairs and to decay into an electron + quark with branching ratio β. No leptoquark candidates were found. We obtain cross section times branching ratio limits as a function of leptoquark mass. For pair production of scalar leptoquarks, we set a leptoquark mass limit of 133 GeV for β=1 and 120 GeV for β=0.5 at 95% confidence level

[en] The WWγ gauge boson couplings were measured using p bar p→lνγ+X (l=e,μ) events at √s=1.8 TeV observed with the D0 detector at the Fermilab Tevatron Collider. The signal, obtained from the data corresponding to an integrated luminosity of 13.8pb^-1, agrees well with the standard model prediction. A fit to the photon transverse energy spectrum yields limits at the 95% confidence level on the CP-conserving anomalous coupling parameters of -1.6<Δκ<1.8 (λ=0) and -0.6<λ<0.6 (Δκ=0). Similar limits are obtained for the CP-violating coupling parameters

[en] First experimental results are presented from a search for events with a rapidity gap between jets. The D0 detector was used to examine events produced by the Fermilab Tevatron p bar p collider at √s =1.8 TeV. The fraction of events with an observed rapidity gap between the two highest transverse energy (E_T) jets is measured as a function of the pseudorapidity separation between the jet edges (Δη_c). An upper limit at the 95% confidence level of 1.1x10^-2 is obtained on the fraction of events with non particles between the jets, for events with Δη_c>3 and jet E_T greater than 30 GeV

[en] The inclusive cross sections times leptonic branching ratios for W and Z boson production in p bar p collisions at √s=1.8 TeV were measured using the D0 detector at the Fermilab Tevatron collider: σ_WB(W→eν)vmkid=double-prime vm1 double-prime= 2.36±0.07±0.13nbσ_WB(W→μν)vmkid=double-prime vm1 double-prime= 2.09±0.23±0.11nbσ_ZB(Z→e⁺e^-)vmkid= double-prime vm1 double-prime= 0.218±0.011±0.012nbσ_ZB(Z→μ⁺μ^-)vmkid= double-prime vm1 double-prime=0.178±0.030±0.009nb. The first error is the combined statistical and systematic uncertainty, and the second reflects the uncertainty in the luminosity. For the combined electron and muon analyses we find σ_WB(W→lν)/σ_ZB(Z→l⁺l^-)=10.90±0.49. Assuming standard model couplings, this result is used to determine the width of the W boson, Γ(W)=2.044±0.093GeV

[en] We present results on the search for the top quark in p bar p collisions at √s =1.8 TeV with an integrated luminosity of 13.5±1.6 pb^-1. We have considered t bar t production in the standard model using electron and muon dilepton decay channels (t bar t→eμ+jets, ee+jets, and μμ+jets) and single-lepton decay channels (t bar t→e+jets and μ+jets) with and without tagging of b quark jets. An analysis of these data optimized for top quark masses below 140 GeV/c² gives a lower top quark mass limit of 128 GeV/c². An analysis optimized for higher top quark masses yields 9 events with an expected background of 3.8±0.9. If we assume that the excess is due to t bar t production, and assuming a top quark mass of 180 GeV/c², we obtain a cross section of 8.2±5.1 pb

[en] The D0 Collaboration reports on a search for the standard model top quark in p bar p collisions at √s=1.8TeV at the Fermilab Tevatron with an integrated luminosity of approximately 50pb^-1. We have searched for t bar t production in the dilepton and single-lepton decay channels with and without tagging of b-quark jets. We observed 17 events with an expected background of 3.8±0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2x10^-6 (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measured its mass to be 199_-21⁺¹⁹ (stat) ±22 (syst) GeV/c² and its production cross section to be 6.4±2.2pb

[en] We report a measurement of the inclusive muon and b-quark production cross sections in p bar p collisions at √s=1.8 TeV using the D0 detector at the Fermilab Tevatron collider. The inclusive muon spectrum extends over the kinematic range |y^μ|<0.8 and 3.5< p_T^μ<60GeV/c, and is well described by the expected contributions from various known sources. The b-quark production cross section for |y^b|<1.0 and p^b_T>6GeV/c is extracted, and agrees with next-to-leading order QCD predictions within the experimental and theoretical uncertainties

[en] The ratio of the number of W+1 jet to W+0 jet events is measured with the D0 detector using data from the 1992--93 Tevatron Collider run. For the W→eν channel with a minimum jet E_T cutoff of 25 GeV, the experimental ratio is 0.065±0.003(stat)±0.007(syst). Next-to-leading order QCD predictions for various parton distributions agree well with each other and are all over 1 standard deviation below the measurement. Varying the strong coupling constant α_s in both the parton distributions and the partonic cross sections simultaneously does not remove this discrepancy. copyright 1995 The American Physical Society

[en] We present new results on the search for the top quark in p bar p collisions at √s=1.8 TeV with an integrated luminosity of 13.5±1.6 pb^--1. We have considered t bar t production in the standard model using electron and muon dilepton decay channels (t bar t→eμ+ jets, ee+ jets, and μμ+ jets) and single-lepton decay channels (t bar t→e+ jets and μ+ jets) with and without tagging of b quark jets. From all channels we have nine events with an expected background of 3.8±0.9. If we assume that the excess is due to t bar t production, and assume a top mass of 180 GeV/c², we obtain a cross section of 8.2±5.1 pb