5 research outputs found
A Study of Event Shapes and Determinations of alpha_s using data of e^+e^- Annihilations at sqrt{s} = 22 to 44 GeV
Data recorded by the JADE experiment at the PETRA e^+e^- collider were used
to measure the event shape observables thrust, heavy jet mass, wide and total
jet broadening and the differential 2-jet rate in the Durham scheme. For the
latter three observables, no experimental results have previously been
presented at these energies. The distributions were compared with resummed QCD
calulations (O(alpha_s^2)+NLLA), and the strong coupling constant alpha_s(Q)
was determined at different energy scales Q=sqrt{s}. The results,
\alpha_s(22 GeV) = 0.161 ^{+0.016}_{-0.011},
\alpha_s(35 GeV) = 0.143 ^{+0.011}_{-0.007},
\alpha_s(44 GeV) = 0.137 ^{+0.010}_{-0.007}, are in agreement with previous
combined results of PETRA albeit with smaller uncertainties. Together with
corresponding data from LEP, the energy dependence of alpha_s is significantly
tested and is found to be in good agreement with the QCD expectation.
Similarly, mean values of the observables were compared to analytic QCD
predictions where hadronisation effects are absorbed in calculable power
corrections.Comment: 36 pages, LaTeX2e, 34 .eps-files included, submitted to Z. Phys. C,
revised version, with comments of referee included and some typos corrected,
accepted for publicatio
Event shapes in e+e- annihilation and deep inelastic scattering
This article reviews the status of event-shape studies in e+e- annihilation
and DIS. It includes discussions of perturbative calculations, of various
approaches to modelling hadronisation and of comparisons to data.Comment: Invited topical review for J.Phys.G; 40 pages; revised version
corrects some nomenclatur
A study of event shapes and determinations of Alpha s using data of e+e- annihilations at Wurzel Sigma = 22 GeV to 44 GeV
A study of event shapes and determinations of Alpha s using data of e+e- annihilations at Wurzel Sigma = 22 GeV to 44 GeV
QCD analyses and determinations of alpha(s) in e+ e- annihilation at energies between 35-GeV and 189-GeV
We employ data taken by the JADE and OPAL experiments for an integrated QCD
study in hadronic e+e- annihilations at c.m.s. energies ranging from 35 GeV
through 189 GeV. The study is based on jet-multiplicity related observables.
The observables are obtained to high jet resolution scales with the JADE,
Durham, Cambridge and cone jet finders, and compared with the predictions of
various QCD and Monte Carlo models. The strong coupling strength, alpha_s, is
determined at each energy by fits of O(alpha_s^2) calculations, as well as
matched O(alpha_s^2) and NLLA predictions, to the data. Matching schemes are
compared, and the dependence of the results on the choice of the
renormalization scale is investigated. The combination of the results using
matched predictions gives alpha_s(MZ)=0.1187+{0.0034}-{0.0019}. The strong
coupling is also obtained, at lower precision, from O(alpha_s^2) fits of the
c.m.s. energy evolution of some of the observables. A qualitative comparison is
made between the data and a recent MLLA prediction for mean jet multiplicities.Comment: 49 pages, 17 figures, submitted to Eur.Phys.J.