P. Laurikainen

Experimental studies on multijet production ine+e− annihilation at PETRA energies

Hadronic jet production bye+e−-annihilation has been studied in the energy range of 14.0–46.7 GeV. The data have been analysed in terms of a cluster algorithm and other topological quantities. The results are compared with 2nd order QCD calculations which incorporate models for the fragmentation of quarks and gluons into hadrons. At the higher energies we observe more spherical and 4-jet like events than predicted by these calculations. We cannot achieve a simultaneous description of the observed 3- and 4-jet production by adjusting the strong coupling constant αs or the fragmentation parameters of the 2nd order QCD models. The observed excess of spherical events can partially be explained by the production of multi-parton events expected from higher order QCD contributions. Consequences of the presented results for the value of αs, determined in previous analyses, are discussed. QCD parton shower models, including soft gluon interference, are able to describe the observed number of spherical events.

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.

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.

Determination of semi-muonic branching ratios and fragmentation functions of heavy quarks ine+e− annihilation at\(\langle \sqrt s \rangle \)=34.6 GeV

AbstractMuon inclusive multihadronic final states ine+e− annihilation at

A study of photon production in hadronice+e− annihilation

\langle \sqrt s \rangle

Tests of the Standard Model in Leptonic Reactions at {PETRA} Energies

=34.6 GeV, collected by the JADE detector at PETRA, have been analysed in terms of the semi-muonic branching ratios and fragmentation functions of heavy quarks. Defining the fragmentation variable, ζ, as

A measurement of the total cross section and a study of inclusive muon production for the process e+e−→ hadrons in the energy range between 39.79 GeV and 46.78 GeV

z = \frac{{\left( {E + p_\parallel } \right)_{hadron} }}{{\left( {E + p} \right)_{quark} }}