[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 performed a direct search for the anomalous ZZγ and Zγγ couplings by studying p bar p→llγ+X (l=e,μ) events at √s=1.8 TeV with the D0 detector at the Fermilab Tevatron Collider. A fit to the transverse energy spectrum of the photon in the signal events, based on the data set corresponding to an integrated luminosity of 14.3pb^-1 (13.7pb^-1) for the electron (muon) channel, yields the following 95% confidence level limits on the anomalous CP-conserving ZZγ couplings: |h₃₀^Z|<1.8 (h₄₀^Z=0) and |h₄₀^Z|<0.5 (h₃₀^Z=0), for a form-factor scale Λ=500 GeV. Limits for the Zγγ couplings and CP-violating couplings are also discussed

[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] The results of a search for W boson pair production in p bar p collisions at √s=1.8 TeV with subsequent decay to dilepton (eμ,ee, and μμ) channels are presented. One event is observed with an expected background of 0.56±0.13 events with an integrated luminosity of approximately 14pb^-1. Assuming equal strengths for the WWZ and WWγ gauge boson coupling parameters κ and λ, limits on the CP-conserving anomalous coupling constants are -2.6<Δκ<2.8 and -2.1<λ<2.1 at the 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] We present a search for events consistent with the production and decay of the squarks and gluinos of the minimal supersymmetric standard model (MSSM) in the D0 detector at the Fermilab Tevatron p bar p collider. We examined data for events containing large missing transverse energy and three or more jets. We observed no excess of events above the expected yield from standard model processes. For a choice of MSSM parameter values, we set a lower limit at the 95% confidence level on the mass of the gluino of 144 GeV/c² for all squark masses and a lower limit of 212 GeV/c² for equal squark and gluino masses

[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 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