4 research outputs found
Measurement of the longitudinal and transverse cross-section in e^+e^- annihilation at sqrt(s)=35-44 GeV
An investigation of the polar angle distribution of charged hadrons is
presented using data taken by the JADE experiment at the PETRA e^+e^- collider
at centre-of-mass energies of 35 and 44 GeV. From fits to the polar angle
distribution the longitudinal, sigma_L, and transverse, sigma_T, cross-section
relative to the total hadronic are determined at an average energy scale of
36.6 GeV. The results are sigma_L/sigma_tot = 0.067 +/- 0.013,
sigma_T/sigma_tot = 0.933 -/+ 0.013 where total errors are given and the
results are exactly anti-correlated. Using the next-to-leading order QCD
prediction for the longitudinal cross-section, the value alpha_S(36.6 GeV) =
0.150 +/- 0.025 of the strong coupling constant is obtained in agreement with
the world average value of alpha_S evolved to an energy scale of 36.6 GeV.Comment: 12 pages, LaTeX2e, 5 .eps-files included, pennames.sty included,
submitted to Phys. Lett.
Tests of analytical hadronisation models using event shape moments in {\epem} annihilation
Predictions of analytical models for hadronisation, namely the dispersive
model, the shape function and the single dressed gluon approximation, are
compared with moments of hadronic event shape distributions measured in \epem
annihilation at centre-of-mass energies between 14 and 209 GeV. In contrast to
Monte Carlo models for hadronisation, analytical models require to adjust only
two universal parameters, the strong coupling and a second quantity
parametrising nonperturbative corrections. The extracted values of as are
consistent with the world average and competitive with previous measurements.
The variance of event shape distributions is compared with predictions given by
some of these models. Limitations of the models, probably due to unknown higher
order corrections, are demonstrated and discussed.Comment: Ref.s [19,36] added and footnote 1 adjuste
Measurement of the strong coupling alpha(s) from the four-jet rate in e+ e- annihilation using JADE data
Data from e+e- annihilation into hadrons collected by the JADE experiment at centre-of-mass energies between 14 GeV and 44 GeV are used to study the four-jet event production rate as a function of the Durham jet algorithm’s resolution parameter ycut. The four-jet rate is compared to QCD next-to-leading order calculations including resummation of large logarithms in the next-to-leading logarithmic approximation. The strong coupling measured from the four-jet rate is αS(MZ0)=0.1159±0.0004(stat.)±0.0012(exp.)±0.0024(had.)±0.0007(theo.) in agreement with the world average