R.D. Heuer

Observation of planar three-jet events in e+e− annihilation and evidence for gluon bremsstrahlung

Abstract Topological distributions of charged and neutral hadrons from the reaction e+e− → multihadrons are studied at √s of about 30 GeV. An excess of planar events is observed at a rate which cannot be explained by statistical fluctuations in the standard two-jet process. The planar events, mostly consisting of a slim jet on one side and a broader jet on the other, are shown actually to possess three-jet structure by demonstrating that the broader jet itself consists of two collinear jets in its own rest system. Detailed agreement between data and predictions is obtained if the process e + e − →q q g is taken into account. This strongly suggests gluon bremsstrahlung as the origin of the planar three-jet events. By comparison of the data with the qqg-model we obtain a value for the strong coupling constant of αS(q2 = 0.17 ± 0.04.

Total cross section for hadron production by e+e− annihilation at petra energies

Abstract The cross section for the process e+e− → multihadrons has been measured at the highest PETRA energies. We measure R (the total cross section in units of the point-like e+e- → μ+μ- cross section) to be 2.9 ± 0.7, 4.0 ± 0.5, 4.6 ± 0.4 and 4.2 ± 0.6 at s of 22, 27.7, 30 and 31.6 GeV, respectively. The observed average multiplicity, together with existing low energy data, indicate a rapid increase in multiplicity with increasing energy.

EXPERIMENTAL-STUDY OF JETS IN ELECTRON-POSITRON ANNIHILATION

Abstract Data on hadron production by e + e − -annihilation at c.m. energies between 30 GeV and 36 GeV are presented and compared with two models both based on first-order QCD but using different schemes for the fragmentation of quarks and gluons into hadrons. In one model the fragmentation proceeds along the parton momenta, in the other along the colour-anticolour axes. The data are reproduced better by fragmentation along the colour axes.

Test of Quantum Electrodynamics at {PETRA}

Differential cross sections for the reactions e+e− → e+e− and e+e− → γγ are given for energies between 27.7 and 31.6 GeV. The results agree with the predictions of standard quantum electrodynamics and set lower limits to the usual cut-off parameters of up to 104 GeV. A limit on the Weinberg angle, sin2θW < 0.63, is obtained at unprecedentedly high q2.

A measurement of the electroweak induced charge asymmetry in e+e−→bb̄☆

Abstract The forward-backward charge asymmetry for the process e + e − → b b → μ ± + hadrons has been measured using the JADE detector at PETRA. An asymmetry of (−22.8 ± 6.0 ± 2.5)% was observed at an average center of mass energy of 34.6 GeV. For comparison, an asymmetry of −25.2% is expected on the basis of the standard Glashow-Salam-Weinberg model.

Experimental evidence for differences in 〈p⊥〉 between quark jets and gluon jets

Abstract We want to dedicate this work to our friend Peter Dittman who contributed so much to the JADE experiment and who died on 31.8.1982.

BARYON PRODUCTION IN E+E(-)-ANNIHILATION AT PETRA

Abstract Data on p and Λ production by e + e − -annihilation at CM energies between 30 and 36 GeV are presented. Indication for an angular anticorrelation in events with baryon-antibaryon pairs is seen.

PRECISE MEASUREMENT OF TOTAL CROSS SECTIONS FOR THE PROCESS e+e - ~ MULTIHADRONS IN THE CM ENERGY RANGE BETWEEN 12.0 AND 36.4 GeV

The total cross section for the process e+e− → hadrons has been measured in the CM energy range between 12.0 and 36.4 GeV using the JADE detector with a typical systematic error of ±3%. The ratio is found to be constant over this range with an average value of 3.97 ± 0.05 (statistical and point-to-point systematic error) ± 0.10 (normalization error). The data were compared with the standard electro-weak interaction model including QCD corrections.

Observation of a charge asymmetry in e+e− → μ+μ−

The angular distribution and the s dependence of the total cross section for the process e+e− → μ+μ− have been measured using the JADE detector at PETRA. After radiative corrections, a forward-backward asymmetry of −(11.8±3.8) % was observed at an average centre of mass energy of 33.5 GeV. For comparison, an asymmetry of −7.8 % is expected on the basis of the standard Glashow-Salam-Weinberg model.

Measurement of the branching ratios for the decays J/ψ → ϱπ and J/ψ → γη′

Abstract Decays of the J/ψ (3.1) resonance into final states with two charged hadrons and two photons are investigated. Branching ratios for the decays J/ψ → ϱπ and J/ψ → γη′ are determined to be Г(J/ψ → pφ) Г(J/ψ → all) = (1.0± 0.2) ·10 −2 , Г(J/ψ → γη′) ГJ/ψ → all) = (2.0± 0.7) · −3 Upper limits for the same decay modes of ψ′ (3.7) are also determined.