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.
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.
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.
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
The polarization of 103 211 Ω− hyperons produced in 800 GeV proton-beryllium inclusive reactions has been measured. Between 0.3<xF<0.7 and 0.5<pt<1.3 GeV/c, the Ω− polarization is found to be consistent with zero, with a mean value of -0.01±0.01 at 〈xF〉=0.5 and 〈pt〉=0.95 GeV/c. This behavior is similar to that of Λ¯0, which also does not have any quarks in common with the incident proton, but is different from Ξ¯+, which is significantly polarized in the same kinematic region.
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.
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.
New measurements are reported of total cross sections for π ± , K ± , p and p on protons and deuterons at 11 momenta between 23 and 280 GeV/ c .
We have measured correlations between single high- p T (1.5< p T <3.5 GeV/ c ) trigger particles on one side of the beam line and groups of particles entering a calorimeter on the opposite side of the beam line. The mean transverse momentum measured in the calorimeter is found to increase with the trigger-particle transverse momentum. The coplanarity of the events increases with trigger-particle transverse momentum. We have compared our data with the predictions of a phenomenological four-jet model. To fit our data we find that we must give large (0.9 GeV/ c ) mean transverse momenta to the constituents of the initial hadrons.
The global topologies of inclusive three-- and four--jet events produced in $\pp$ interactions are described. The three-- and four--jet events are selected from data recorded by the D\O\ detector at the Tevatron Collider operating at a center--of--mass energy of $\sqrt{s} = 1800$ GeV. The measured, normalized distributions of various topological variables are compared with parton--level predictions of tree--level QCD calculations. The parton--level QCD calculations are found to be in good agreement with the data. The studies also show that the topological distributions of the different subprocesses involving different numbers of quarks are very similar and reproduce the measured distributions well. The parton shower Monte Carlo generators provide a less satisfactory description of the topologies of the three-- and four--jet events.
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