The inclusive production of D ∗± mesons in single tagged photon-photon collisions is investigated using the JADE detector at PETRA. D ∗± mesons are reconstructed through their decay into D 0 +π ± where the D 0 decays via D 0 →Kππ 0 . The event rate and topology are compared to the expectations of c quark production in the quark-parton model: γγ→c c .
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Results on hyperon production are reported for data accumulated at 10 GeV centre-of-mass energy with the ARGUS detector. Signals for both the octet states Λ, Σ 0 and Ξ − and the decuplet states Σ ± (1385), Ξ 0 (1530) and Ω − are observed 1 (references to a specific state are to be interpreted as also implying the charge conjugate state), some for the first time in e + e − annihilation. Baryon rates from γ dir (1S) decays are enhanced by a factor of about 3 over the continuum.
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We report measurements of two-particle correlations in rapidity space between a p¯ or Λ¯ and an additional p, p¯, Λ, or Λ¯. We find evidence for local conservation of baryon number, and for the first time observe a pronounced anticorrelation between baryons with the same value of baryon number. Such an anticorrelation is expected in fragmentation models where the rapidity order of particles closely reflects their ‘‘color order,’’ as is the case, for example, in recent versions of the Lund string model.
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We report a measurement of the inclusive D/D̄ production cross section in 800 GeV/ c proton-proton interactions. The experiment used the high resolution bubble chamber LEBC exposed to an 800 GeV/ c proton beam at the Fermilab MPS. We obtain σ( D/ D ̄ )=59 −15 +22 μ b (statistical errors), having analysed 25% of the total data sample. Comparison with 400 GeV/ c pp dat a obtained with LEBC at CERN shows a D/D̄ cross section increase by a factor of 1.7 −0.5 +0.7 . This is in good agreement with fusion model calculations.
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A comparison is made between the properties of the final state hadrons produced in 280 GeV μp interactions and ine+e− annihilation. The Lund model of hadroproduction is used as an aid in understanding the differences observed. The hadron distributions from μp ande+e− interactions are consistent with the quark parton model assumption of environmental independence, provided that the differences in heavy quark production and hard QCD effects in the two processes are taken into account. A comparison with aK+p experiment is also made. Values are also determined for the Lund model parameters σq = 0.410 ± 0.002 ± 0.020 GeV and σ′ = 0.29−0.15 −0.13+0.09+0.10 GeV, controlling the transverse momenta in fragmentation and intrinsic transverse momenta of the struck quark respectively.
With respect to the virtual photon axis.
With respect to the sphericity axis.
With respect to the thrust axis.
Inclusive Ξ− production in e+e− annihilation at 29 GeV has been measured with the Mark II detector. From an integrated luminosity of 207 pb−1, we determine a production rate of 0.017±0.004±0.004 Ξ−+Ξ¯+ per hadronic event. A search for Ξ*0(1530)→Ξ−π+ leads to an upper limit of N(Ξ*0)/N(Ξ−)<0.35 at a 90% confidence level.
Numerical values supplied by S. Klein.
Extrapolation over full x range using LUND Monte Carlo.
A forward-backward asymmetry A , consistent with that expected from the γ − Z 0 interference term in the process e + e − → q q , is observed in the laboratory production angular distribution of high-momentum ∧ baryons. The data were collected with the High Resolution Spectrometer at PEP. The asymmetry for ∧ baryons with fractional energy z= 2E s greater than 0.3 is A = (−23± 8 plusmn ; 2)%.
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Data read from graph.
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VALUES OBTAINED USING ASSUMPTION R=0.
VALUES OBTAINED USING ASSUMPTION R=0.
TheA-dependence of the polarization ofΛ0,s produced inclusively in neutron-nucleus interactions at a mean neutron momentum of about 40 GeV/c has been measured in an experiment performed using the BIS-2 spectrometer at the Serpukhov accelerator. Carbon, Aluminium and Copper targets were used. TheΛ0,s were produced in the kinematical region of 0.6<pT<1.3 GeV/c and 0.2<xF<0.9. Describing the polarization of theΛ0,s by ℘=a·A a value of (−0.15+0.07/−0.60) was obtained by a fit to our data.
POLARIZATION IS DESCRIBED BY A POWER LOW: POL = C*A**B, WHERE C = -1.1, +0.4, -0.3 , A- ATOMIC NUMBER AND B = -0.15, +0.07, -0.6.
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