Adriani, O.
Cross Section
DN/DSPHERICITY
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rivet Analysis
A study of the energy evolution of event shape distributions and their means with the DELPHI detector at LEP.

The DELPHI collaboration Abdallah, J. ; Abreu, P. ; Adam, W. ; et al.
Eur.Phys.J.C 29 (2003) 285-312, 2003.
Inspire Record 620250 DOI 10.17182/hepdata.13029

Infrared and collinear safe event shape distributions and their mean values are determined in e+e- collisions at centre-of-mass energies between 45 and 202 GeV. A phenomenological analysis based on power correction models including hadron mass effects for both differential distributions and mean values is presented. Using power corrections, alpha_s is extracted from the mean values and shapes. In an alternative approach, renormalisation group invariance (RGI) is used as an explicit constraint, leading to a consistent description of mean values without the need for sizeable power corrections. The QCD beta-function is precisely measured using this approach. From the DELPHI data on Thrust, including data from low energy experiments, one finds beta_0 = 7.86 +/- 0.32 for the one loop coefficient of the beta-function or, assuming QCD, n_f = 4.75 +/- 0.44 for the number of active flavours. These values agree well with the QCD expectation of beta_0=7.67 and n_f=5. A direct measurement of the full logarithmic energy slope excludes light gluinos with a mass below 5 GeV.

71 data tables
Table 1

1-THRUST distribution.

Table 2

THRUST-MAJOR distribution.

Table 3

THRUST-MINOR distribution.

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rivet Analysis
Studies of quantum chromodynamics with the ALEPH detector

The ALEPH collaboration Barate, R. ; Buskulic, D. ; Decamp, D. ; et al.
Phys.Rept. 294 (1998) 1-165, 1998.
Inspire Record 428072 DOI 10.17182/hepdata.47582

Previously published and as yet unpublished QCD results obtained with the ALEPH detector at LEP1 are presented. The unprecedented statistics allows detailed studies of both perturbative and non-perturbative aspects of strong interactions to be carried out using hadronic Z and tau decays. The studies presented include precise determinations of the strong coupling constant, tests of its flavour independence, tests of the SU(3) gauge structure of QCD, study of coherence effects, and measurements of single-particle inclusive distributions and two-particle correlations for many identified baryons and mesons.

44 data tables
Table 1

Charged particle sphericity distribution.

Table 2

Charged particle aplanarity distribution.

Table 3

Charged particle Thrust distribution.

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Properties of hadronic Z decays and test of QCD generators

The ALEPH collaboration Buskulic, D. ; Decamp, D. ; Goy, C. ; et al.
Z.Phys.C 55 (1992) 209-234, 1992.
Inspire Record 334577 DOI 10.17182/hepdata.1420

Distributions are presented of event shape variables, jet roduction rates and charged particle momenta obtained from 53 000 hadronicZ decays. They are compared to the predictions of the QCD+hadronization models JETSET, ARIADNE and HERWIG, and are used to optimize several model parameters. The JETSET and ARIADNE coherent parton shower (PS) models with running αs and string fragmentation yield the best description of the data. The HERWIG parton shower model with cluster fragmentation fits the data less well. The data are in better agreement with JETSET PS than with JETSETO(αS2) matrix elements (ME) even when the renormalization scale is optimized.

41 data tables
Table 1

Sphericity distribution.

Table 2

Sphericity distribution.

Table 3

Aplanarity distribution.

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