The polarization of Ξ¯ + hyperons produced by 800-GeV/c protons in the inclusive reaction p+Be→Ξ¯ ++X has been measured. The average polarization of the Ξ¯ +, at a mean xF=0.39 and pt=0.76 GeV/c, is -0.097±0.012±0.009. The magnetic moment of the Ξ¯ + is 0.657±0.028±0.020 nuclear magneton.
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With a data sample containing 1.1×105 J/ψ→μ+μ− decays reconstructed with 16 MeV/c2 rms mass resolution, we have measured the differential cross sections versus Feynman-x, rapidity, and pT for the production of J/ψ and ψ’ in 800 GeV/c p-Au collisions. Our results are compared with leading-order QCD predictions and with previous measurements. While the shapes of the cross sections are in qualitative agreement with QCD predictions, the magnitudes disagree by factors of 7 (J/ψ) and 25 (ψ’). Assuming an appropriate form for the differential cross sections in regions not measured we derive a total J/ψ production cross section σ(p+N→J/ψ+X)=442±2±88 nb/nucleon and a (model-dependent) total ψ’ cross secton σ(p+N→ψ’+X)=75±5±22 nb/nucleon. For J/ψ produced at central rapidity, dσ(p+N→J/ψ+X)/dy‖y=0=230±5±46 nb/nucleon.
Extrapolated measured total cross sections.
J/PSI cross section at central rapidity.
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Using a silicon-microstrip detector array to identify secondary vertices, we have observed b→J/ψ→μ+μ− decays in 800GeV/c proton-gold interactions. The doubly differential cross section for J/ψ mesons originating from b-quark decays, assuming linear dependence on nucleon number, is d2σ/dxFdpT2=107±28±19[pb/(GeV/c)2]/nucleon at xF=0.05 and pT=1GeV/c. This measurement is compared to next-to-leading-order QCD predictions. The integrated b-quark production cross section, obtained by extrapolation over all xF and pT, is σ(pN→bb¯+X)=5.7±1.5±1.3 nb/nucleon.
All J/PSI(1S) are from B/BBAR decays. Cross section per nucleon was obtained with linear A-dependence.
Cross section per nucleon was obtained with linear A-dependence.
All J/PSI(1S) are from B/BBAR decays. Cross section per nucleon was obtained with linear A-dependence. Extrapolation in the XL=0.05 and PT=1 GEV bin.
The differential cross sections dσ/dxF for J/ψ produced inclusively in 800 GeV/c p-Cu and p-Be collisions have been measured in the kinematic range 0.30≤xF≤0.95 through the decay mode J/ψ→μ+μ−. They are compared with the predictions of the semilocal duality model for several sets of parton density functions. No evidence for a suggested intrinsic charm contribution to the cross section is observed. The ratio of the differential cross sections for Cu and Be targets confirms the suppression of J/ψ production in heavy nuclei at large xF.
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The polarization of 103 211 Ω− hyperons produced in 800 GeV proton-beryllium inclusive reactions has been measured. Between 0.3
Omega- polarization at the target.
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The nuclear dependence for 800 GeV/c proton production of neutron D mesons has been measured near xF=0 in Experiment 789 at Fermilab. D mesons from beryllium and gold targets were detected with a pair spectrometer and a silicon vertex detector via their decay D→Kπ. No nuclear dependence is found, with a measured α=1.02±0.03±0.02. The measured differential cross section, dσ/dxF, for neutral-D-meson production at 〈xF〉=0.031 is 58±3±7 μb/nucleon. The integrated cross section obtained by extrapolation of the measured cross section to all xF is 17.7±0.9±3.4 μb/nucleon and is consistent with previous measurements.
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With 4.36×106 events, spin precession in a magnetic field has been used to measure the magnetic moment of the Ξ− hyperon as -0.6505±0.0025 nuclear magnetons.
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The polarization PΞ− of Ξ− hyperons produced by 800-GeV protons has been measured for xF from 0.3 to 0.7 and pT from 0.5 to 1.5 GeV/c. PΞ− has a pT dependence similar to that of the Λ but has a different xF behavior. Also, an energy dependence of PΞ− has been observed.
1.3 mv production angle was horizontal. Others are vertical.
The nuclear dependence for 800 GeV/c proton production of J/ψ’s has been measured near xF=0. $J/ psi—’s produced from beryllium, carbon, and tungsten targets were detected with the Fermilab E789 pair spectrometer. These data extend the results from E772 down to the range xF=-0.1 to 0.1 and indicate a gradually increasing suppression as xF falls below zero.
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A sample of 24 700 Ω− hyperons was produced by a prolarized neutral beam in a spin-transfer reaction. The Ω− polarizations are found to be -0.054±0.019 and -0.149±0.055 at mean Ω− momenta of 322 and 398 GeV/c, respectively. The directions of these polarizations give an Ω− magnetic moment of -(1.94±0.17±0.14)μN
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