M. Nozaki

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.

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.

Measurements of energy correlations ine+e−→hadrons

Energy-energy-correlations (EEC) have been measured with the JADE detector at c.m. energies of 14 GeV, 22 GeV and in the region 29 GeV<Ecm<36 GeV. Corrected results are presented of EEC and their asymmetry, which can be directly compared to theoretical predictions. At 〈Ecm〉=34 GeV a comparison with second order QCD predictions yields good agreement for the string model fragmentation resulting in a value of the strong coupling constant αs=0.165±0.01 (stat.). The independent fragmentation models, which yield values of αs between 0.10 and 0.15 depending on the treatment of energy and momentum conservation and of the gluon splitting, do not provide a satisfactory description of the data over the full angular range.

Particle distribution in 3-jet events produced bye−e−-annihilation

We have studied the distribution of particles within and between jets of 3-jet final states produced in the reactione+e−→hadrons at c.m. energies of 22 GeV and 29–36.4 GeV. The lowest energy jet shows distributions of transverse momenta, particle flow, and energy flow which differ significantly from those of the other two jets and from jets of 2-jet events atEcm=14 GeV. First order QCD calculations with subsequent fragmentation of quarks and gluons into hadrons indicate that the lowest energy jet has the largest probability of originating from a gluon. To reproduce the observed differences in an independent parton fragmentation model, the secondary quarks of a gluon jet have to have higher transverse momenta and lower parallel momenta than those of a quark jet. The particle densities between the jets as well as the correlation of transverse and longitudinal momenta of the particles within the jets favour models with fragmentation along the colour axes.

Test of Fragmentation Models by Comparison with Three Jet Events Produced in e+ e- ---> Hadrons

Abstract The energy flow and particle flow distributions of planar three-jet events produced in e+e−→ hadrons at CM energies between 29.5 and 36.4 GeV have been interpreted in terms of the reactions e+e−→q q g and compared with the distributions calculated from two different fragmentation schemes, one based on independent parton fragmentation, the other one on fragmentation along colour flux lines. The particle density at angles between the two highest energy jets is found to decrease more strongly with increasing transverse mass of the particles than the particle density at angles between any of these jets and the lowest energy jet. The high momentum particles within the two most energetic jets are emitted at larger angles with respect to the lowest energy jet than the average particles. These observations are well reproduced by fragmentation along colour flux lines, but not by independent parton fragmentation.

Measurement of the processese+e−→e+e− ande+e−→γγ at PETRA

AbstractCross sections for the reactionse+e−→e+e− (Bhabha scattering) ande+e−→γγ are measured for center-of-mass (c.m.) energies

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