η production has been investigated by the Mark II collaboration at the SLAC e+e− storage ring PEP. η particles are reconstructed by their γγ decay mode. The η fragmentation function has been measured and found to be in good agreement with the Lund-model prediction. η′ production has been measured for the first time in high-energy e+e− annihilation. There is evidence at the 3σ level for Ds± decay into ηπ± and η′π±.
Numerical values supplied by G.Wormser.
Z = 0.0 point extrapolated using LUND fragmentation model.
Z = 0.0 point extrapolated using LUND fragmentation model.
The Brookhaven Alternating Gradient Synchrotron polarized proton beam incident on a beryllium target was used for inclusive Λ production at beam momenta of 13.3 and 18.5 GeV/c. The beam polarization was transverse to the beam direction with magnitude 0.63 at 13.3 GeV/c and 0.40 at 18.5 GeV/c. The Λ polarization was measured and found to be in agreement with results from earlier experiments which used unpolarized proton beams. Analyzing power AN and spin transfer DNN of the Λ’s were both measured and compared with a hyperon-polarization model in which the polarization arises from a Thomas-precession effect. There is good agreement with its predictions: AN=0 and DNN=0. In particular, our measurement of 〈DNN〉=-0.009±0.015 supports the idea that the valence quarks carry all of the hadron spin, since this assumption is implicit in the model’s use of SU(6) wave functions to form final-state hadrons from beam fragments and sea quarks. The presence of substantial KS samples at both beam momenta and Λ¯’s at 18.5 GeV/c prompted a measurement of their analyzing powers, which yielded AN(KS)=-0.094±0.012 at 13.3 GeV/c beam momentum and -0.076±0.015 at 18.5 GeV/c, and AN(Λ¯)=0.03±0.10.
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The cross section of the quasi-elastic reactions\(\bar v_\mup \to \mu ^ +\Lambda (\Sigma ^0 )\) in the energy range 5–100 GeV is determined from Fermilab 15′ bubble chamber antineutrino data. TheQ2 analysis of quasi-elastic Λ events yieldsMA=1.0±0.3 GeV/c2 for the axial mass value. With zero µΛK0 events observed, the 90% confidence level upper limit\(\sigma (\bar v_\mup \to \mu ^ +\Lambda {\rm K}^0 )< 2.0 \cdot 10^{ - 40} cm^2 \) is obtained. At the same time, we found that the cross section of reaction\(\bar v_\mup \to \mu ^ +\Lambda {\rm K}^0+ m\pi ^0 \) is equal to\(\left( {3.9\begin{array}{*{20}c}{ + 1.6}\\{ - 1.3}\\ \end{array} } \right) \cdot 10^{ - 40} cm^2 \).
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The cross section for the production of π+π− or K+K− pairs in γγ interactions is measured for mππ between 1.7 and 3.5 GeV/c2 and for two intervals of γγ center-of-mass scattering angle. Results are compared with predictions of a QCD model.
Data read off graph.
Data read off graph.
We have measured the K0+K¯ 0 inclusive cross section in e+e− annihilation at 29 GeV with the Mark II detector SLAC PEP. We find 1.27±0.03±0.15 K0+K¯ 0 per hadronic event. We have also used time-of-flight particle identification to measure the K± rate over the momentum range 300–900 MeV/c.
Extrapolated to full momentum range by Monte-Carlo.
Statistical errors only.
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Axis error includes +- 0.0/0.0 contribution (?////NOT GIVEN).
Axis error includes +- 0.0/0.0 contribution (?////NOT GIVEN).
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