H. Kado

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.

Measurement of resonance production in the reactionsγγ →π0π0 andγγ →π0η

AbstractResonance production in the γγ reactionse+e−→e+e+e−π0π0 ande+e−π0η has been studied with the JADE detector at PETRA. The decay widths into γγ of thef2(1270),a0(980) anda2(1320) were measured to be

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

\Gamma _{\gamma \gamma } (f_2 (1270)) = 3.19 \pm 0.09_{ - 0.38}^{ + 0.22}

Measurements of energy correlations ine+e−→hadrons

Kev,Γλλ(a0(980))=0.28±0.04±0.10 KeV/BR(a0(980)→π0η) andΓλλ(a2(1320))=1.01±0.14±0.22KeV. For thef0(975) andf4(2050) upper limits of the widths were obtained,Γλλ(f0(975))<0.6 KeV, andΓλλ(f4(2050))<1.1 KeV, both at the 95% C.L. Assuming that the spin 0 background under thef2(1270) is small, thef2(1270) was found to be produced exclusively in a helicity 2 state. The helicity 0 contribution is <15% at the 95% C.L. The cross section forλλ→π0π0 in the mass range 2.0–3.5 GeV/c2 was measured for the first time. Since the cross section forλλ→π+π− is a factor ∼2 larger, ππ production in this range can be interpreted as taking place via isospin 0 production.

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

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.

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

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.

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

The mean charged multiplicity as well as its distribution has been measured as a function of c.m. energy in the reactione+e−→hadrons. Fragmentation models are compared with the data. After applying radiative corrections the mean charged multiplicity is measured to be 8.4±0.3±0.6 at 12 GeV, 13.1±0.3±0.6 at 30 GeV and 13.6±0.3±0.6 at 35 GeV. The ratio of mean charged multiplicity to the dispersion (/Dch) is almost constant in the energy range studied, indicating KNO scaling of the charged multiplicity. The inclusive differential cross sections(dσ/dxp) shows scaling violation in the highxp region (xp>0.15). The absolute value of the scaling violation is consistent with the result of 2nd order QCD calculations. The production of neutral kaons has been investigated by identifying the decayKS0→π+π−. The production probability for a strange quark relative to that of au ord quark in the fragmentation, γs, has been determined to be 0.27±0.03±0.05 averaged over c.m. energies from 12 to 35 GeV. Momentum spectra for neutral kaons are presented and are compared with model predictions.