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DIFFERENT VALUES FOR SIG CORRESPONDS TO DIFFERENT MODELS.
Total cross sections for Sigma- and pi- on beryllium, carbon, polyethylene and copper as well as total cross sections for protons on beryllium and carbon have been measured in a broad momentum range around 600GeV/c. These measurements were performed with a transmission technique adapted to the SELEX hyperon-beam experiment at Fermilab. We report on results obtained for hadron-nucleus cross sections and on results for sigma_tot(Sigma- N) and sigma_tot(pi- N), which were deduced from nuclear cross sections.
Results for nuclear total cross sections.
Average total cross sections for nucleon targets deduced from the nuclear target data, at the average beam momentum.
We present a measurement of the top quark pair ttbar production cross section in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1} of data collected by the DO detector at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), large missing transverse energy, and at least four jets, and extract the ttbar content of the sample based on the kinematic characteristics of the events. For a top quark mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1} (syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.
TTBAR production cross section from the combined electron+jet and muon+jet channels.
We have searched for production of charmed mesons in the reaction π−+N→D*−+X, D*−→π−+D¯0, D¯0→K++π− at a beam momentum of 10.5 GeV/c. We measure the cross section times branching ratio to be 7±20 nb/nucleon.
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The highest-energy measurement of ΔσL(pp) and the first ever measurement of ΔσL(p¯p), the differences between proton-proton and antiproton-proton total cross sections for pure longitudinal spin states, are described. Data were taken using 200-GeV/c polarized beams incident on a polarized-proton target. The results are measured to be ΔσL(pp)=−42±48(stat)±53(syst) μb and ΔσL(p¯p)=−256±124(stat)±109(syst) μb. Many tests of systematic effects were investigated and are described, and a comparison to theoretical predictions is also given. Measurements of parity nonconservation at 200 GeV/c in proton scattering and the first ever of antiproton scattering have also been derived from these data. The values are consistent with zero at the 10−5 level.
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Results are reported of an experiment to measure the cross section for production of the D*+ (D*−) in 200-GeV/c π−N interactions. We observe 78 ± 26 events corresponding to a D*-production cross section dσdy=1.6±0.5 μb at y=0.
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Results are presented of a measurement of the production of D*+ (D*−) in 250-GeV/c π−N interactions. We observe 2.1±7.8 events corresponding to a charge-D* cross section σ(D*) of 0.4±1.5 μb/nucleon. When averaged with our previous measurement made at 200 GeV/c, the result is σ(D*)=2.3±1.0 μb/nucleon with (dσ/dx)‖x=0=4.6±2.0 μb.
THIS DATA FROM PREVIOUS PUBLICATION : PRL 46, 761 (1981).
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P P data are taken from Adams et al, Fermilab-Pub-91/13-E.
Ratio of the spin averaged invariant cross section for PI0 production in p p and pbar p interactions.
We report the results of first physics runs of the L3 detector at LEP. Based on 2538 hadron events, we determined the mass m z 0 and the width Γ z 0 of the intermediate vector boson Z 0 to be m z 0 =91.132±0.057 GeV (not including the 46 MeV LEP machine energy uncertainty) and Γ z 0 =2.588±0.137 GeV. We also determined Γ invisible =0.567±0.080 GeV, corresponding to 3.42±0.48 number of neutrino flavors. We also measured the muon pair cross section and determined the branching ratio Γ μμ = Γ h =0.056±0.006. The partial width of Z 0 →e + e − is Γ ee =88±9±7 MeV.
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With a sample of about 2000( γ + γ ′+ γ ″) events observed in π-W interactions at 286GeV/ c , the ratio ( γ ′+ γ ″)/ γ =0.51±0.07, the branching ratio times the inclusive total cross section Bσ =(386±17±85) pb per W nucleus, as well as the differential cross sections in χ F and p T have been measured. These results are compared with previous data obtained with the same apparatus at a lower beam momentum (194 GeV/ c ). Both data sets are compared with a theoretical calculation (“duality model”) which also allows one to extract the shape parameter β g of the gluon distribution in the pion. β g is found to be 2.3 −0.3 +0.4 (stat.) −0.5 +0.1 (syst.).
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