Measurements of energy-energy correlations in hadronic final states produced in e + e − annihilation at c.m. energies between 7.7 and 31.6 GeV are presented. The data are compared to perturbative QCD predictions. Good qualitative agreement above 20 GeV c.m. energy is found. The importance of non-perturbative effects is discussed, as well as the detailed behaviour of the correlation near 180°.
Results on inclusive K s 0 production in e + e − annihilation at mean center-of-mass energies of 9.4, 12.0 and 30 GeV are presented. The ratio R (K 0 ) = 2 σ (K s 0 )/ σ μμ rises from 3.10 ± 0.75 at √ s = 9.4 GeV to 5.6 ± 1.2 at √ s = 30 GeV, corresponding to an approximately constant K 0 /charged-particle ratio of 0.12 ± 0.02. A similar ratio for K 0 / charged particle is observed for direct hadronic decays of the ϒ.
The reaction e + e − → hadrons has been measured in the ϒ and ϒ′ region using the DASP detector at the DESY storage ring DORIS. The following final results are obtained: R had (9.5 GeV)=3.73±0.16±0.28, Γ ee ( ϒ )=(1.23 ± 0.08 ± 0.12) keV, B μμ ( ϒ )=(3.2±1.3±0.3)%, Γ ee Γ had Γ tot (ϒ′)=(0.55±0.11 ±0.06) keV , and M ( ϒ ′)− M ( ϒ )=(556 ±10) MeV.
Using the solenoidal magnetic detector PLUTO, we have measured the total cross section for e + e − annihilation into hadrons. Results are presented for center of mass energies between 3.6 and 4.8 GeV, and in the regions of the J ψ (3.1) and ψ(3.7) resonances. We also present results for the 2 prong cross section in the energy range 3.6 to 4.8 GeV.
We have measured the production cross section for K s 0 in e + e − annihilation from 3.6 to 5.0 GeV center of mass energy. A substantial increase of the K s 0 yield is observed around 4 GeV in qualitative agreement with the charm hypothesis.
We report measurements of single-particle inclusive spectra and two-particle correlations in decays of the Υ(1S) resonance and in nonresonant annihilations of electrons and positrons at center-of-mass energy 10.49 GeV, just below BB¯ threshold. These data were obtained using the CLEO detector at the Cornell Electron Storage Ring (CESR) and provide information on the production of π, K, ρ, K*, φ, p, Λ, and Ξ in quark and gluon jets. The average multiplicity of hadrons per event for upsilon decays (compared with continuum annihilations) is 11.4 (10.5) pions, 2.4 (2.2) kaons, 0.6 (0.5) ρ0, 1.2 (0.8) K*, 0.6 (0.4) protons and antiprotons, 0.15 (0.08) φ, 0.19 (0.07) Λ and Λ¯, and 0.016 (0.005) Ξ− and Ξ¯ +. We have also seen evidence for η and f0 production. The most significant differences between upsilon and continuum final states are (1) the inclusive energy spectra fall off more rapidly with increasing particle energy in upsilon decays, (2) the production of heavier particles, especially baryons, is not as strongly suppressed in upsilon decays, and (3) baryon and antibaryon are more likely to be correlated at long range in upsilon decay than in continuum events.
First results from the magnetic detector PLUTO at the new e + e − storage ring PETRA are shown. The ratio R of the cross section for hadron production to that for μ-pair production has been measured to be R = 5.0 ± 0.5 at 13 GeV and 4.3 ±0.5 at 17 GeV. Both values have an additional systematic error of 20%. The events show a typical 2-jet structure. The mean transverse momentum approaches a constant value with increasing energy implying a shrinkage of the jet opening angle.
Using the upgraded Beijing Spectrometer (BESII), we have measured the total cross section for $e^+e^-$ annihilation into hadronic final states at center-of-mass energies of 2.6, 3.2, 3.4, 3.55, 4.6 and 5.0 GeV. Values of $R$, $\sigma(e^+e^-\to {hadrons})/\sigma(e^+e^-\to\mu^+\mu^-)$, are determined.
We report on the first observation of Δ(1232) ++ and Δ(1232)++¯ baryons in e + e − annihilation at energies around 10 GeV, using the ARGUS detector at DORIS II. The sum of the rates of Δ ++ and Δ++¯ per hadronic event in the continuum is measured to be 0.040±0.008±0.006, and the rate in direct ϒ(1S) decays is 0.124±0.016±0.015. The momentum spectrum of Δ ++ baryons in direct ϒ(1S) decays has been measured.
Using the CLEO III detector, we measure absolute cross sections for e+e- --> hadrons at seven center-of-mass energies between 6.964 and 10.538 GeV. The values of R, the ratio of hadronic and muon pair production cross sections, are determined within 2% total r.m.s. uncertainty.
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