703 research outputs found
Tests of Power Corrections to Event Shape Distributions from e+e- Annihilation
A study of differential event shape distributions using e+e- data at
centre-of-mass energies of 35 to 183 GeV is presented. We investigated
non-perturbative power corrections for the thrust, C-parameter, total and wide
jet broadening observables. We observe a good description of the distributions
by the combined resummed QCD calculations plus power corrections from the
dispersive approach. The single non-perturbative parameter \alpha_0 is measured
to be \alpha_0 (2 GeV) = 0.502 +- 0.013 (stat.) ^{+0.046)_{-0.032} (exp. syst.)
^{+0.074}_{-0.053} (theo. syst.) and is found to be universal for the
observables studied within the given systematic uncertainties. Using revised
calculations of the power corrections for the jet broadening variables,
improved consistency of the individual fit results is obtained. Agreement is
also found with results extracted from the mean values of event shape
distributions.Comment: 19 pages, LaTeX2e, 8 .eps-files included, paper contributed to the
EPS-HEP99 conference in Tampere, Finlan
Tests of Power Corrections for Event Shapes in e+e- Annihilation
A study of perturbative QCD calculations combined with power corrections to
model hadronisation effects is presented. The QCD predictions are fitted to
differential distributions and mean values of event shape observables measured
in e+e- annihilation at centre-of-mass energies from 14 to 189 GeV. We
investigate the event shape observables thrust, heavy jet mass, C-parameter,
total and wide jet broadening and differential 2-jet rate and observe a good
description of the data by the QCD predictions. The strong coupling constant
alpha_S(M_Z) and the free parameter of the power correction calculations
alpha_0(2 GeV) are measured to be alpha_S(M_Z) = 0.1171 +/- 0.0032/0.0020 and
alpha_0(2 GeV) = 0.513 +/- 0.066/0.045. The predicted universality of alpha_0
is confirmed within the uncertainties of the measurements.Comment: 28 pages, LaTeX2e, 21 .eps-files included, accepted by Eur. Phys. J.
C-Parameter and Jet Broadening at PETRA Energies
e^+e^- annihilation data recorded by the JADE detector at PETRA were used to
measure the C-parameter for the first time at \sqrt{s}= 35 and 44 GeV. The
distributions were compared to a resummed QCD calculation.
In addition, we applied extended resummed calculations to the total and wide
jet broadening variables, B_T and B_W. We combined the results on \alpha_s with
those of our previous study of differential 2-jet rate, thrust, and heavy jet
mass, obtaining
\alpha_s(35 GeV) = 0.1448 +0.0117 -0.0070 and \alpha_s(44 GeV) = 0.1392
+0.0105 -0.0074.
Moreover power corrections to the mean values of the observables mentioned
above were investigated considering the Milan factor and the improved
prediction for the jet broadening observables.
Our study, which considered e^+e^- data of five event shape observables
between \sqrt{s}= 14 and 183 GeV, yielded \alpha_s(M_{Z^0})=0.1177 +0.0035
-0.0034.Comment: 14 pages, LaTeX2e, 9 .eps-files included, abbreviated version of the
paper contributed to the ICHEP'98 conference in Vancouver, submitted to Phys.
Lett.
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
Study of moments of event shapes 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 were used to study moments of
event shape distributions. The data were compared with Monte Carlo models and
with predictions from QCD NLO order calculations. The strong coupling constant
measured from the moments is alpha_S(M_Z) = 0.1286 +/- 0.0007 (stat) +/- 0.0011
(expt) +/- 0.0022 (had) +/- 0.0068 (theo), alpha_S(M_Z) = 0.1286 +/- 0.0072
(total error), consistent with the world average. However, systematic
deficiencies in the QCD NLO order predictions are visible for some of the
higher moments.Comment: JADE note 147 submitted as contributed paper to ICHEP 2004, corrected
statistical error of 6 observable average and several typo
Measurement of the Strong Coupling Constant 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 were used to study the
four-jet rate as a function of the Durham algorithm's resolution parameter
y_cut. The four-jet rate was compared to a QCD NLO order calculations including
NLLA resummation of large logarithms. The strong coupling constant measured
from the four-jet rate is alpha_S(M_Z) = 0.1169 +/- 0.0004 (stat) +/- 0.0012
(expt) +/- 0.0021 (had) +/- 0.0007 (theo), alpha_S(M_Z) = 0.1169 +/- 0.0026
(total error) in agreement with the world average.Comment: JADE note 146 submitted as contributed paper to ICHEP 200
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