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The scale dependence of the hadron multiplicity in quark and gluon jets and a precise determination of C(A)/C(F).

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.
Phys.Lett.B 449 (1999) 383-400, 1999.
Inspire Record 495414 DOI 10.17182/hepdata.49173

Data collected at the Z resonance using the DELPHI detector at LEP are used to determine the charged hadron multiplicity in gluon and quark jets as a function of a transverse momentum-like scale. The colour factor ratio, \cacf, is directly observed in the increase of multiplicities with that scale. The smaller than expected multiplicity ratio in gluon to quark jets is understood by differences in the hadronization of the leading quark or gluon. From the dependence of the charged hadron multiplicity on the opening angle in symmetric three-jet events the colour factor ratio is measured to be: C_A/C_F = 2.246 \pm 0.062 (stat.) \pm 0.080 (syst.) \pm 0.095 (theo.)

3 data tables
Table 1

Charged multiplicity in events with a hard photon, as a function of the apparent centre-of-mass energy (SQRT(S)) of the hadronic system. The errors shown are statistical only.

Table 2

Charged multiplicity in symmetric three jet events as function of the opening angle between the low energetic jets, THETA1. Jets are defined from charged and neutral particles using the DURHAM algorithm. The errors shown are statistical only.

Table 3

Twice the difference of the multiplicity in three jet events and in qqbar events of comparable scale 2(N_3jet-N_qqbar). The three-jet event multiplicity isequal to the data of Fig. 3c), the qqbar-multiplicity is taken from a fit of th e e+e- data corrected for the varying b-quark contribution. This multiplicity can be identified with the multiplicity of a hypothetical gluon-gluon event. Thereis a normalization uncertainty (i.e. a scale independent constant) of the gluon -gluon event multiplicity which should not influence the slope of the gg-multiplicity with scale (see paper). The errors shown are statistical only.


Determination of alpha-s from hadronic event shapes measured on the Z0 resonance

The L3 collaboration Adrian, O. ; Aguilar-Benitez, M. ; Ahlen, S. ; et al.
Phys.Lett.B 284 (1992) 471-481, 1992.
Inspire Record 334951 DOI 10.17182/hepdata.29157

We present a study of the global event shape variables thrust and heavy jet mass, of energy-energy correlations and of jet multiplicities based on 250 000 hadronic Z 0 decays. The data are compared to new QCD calculations including resummation of leading and next-to-leading logarithms to all orders. We determine the strong coupling constant α s (91.2 GeV) = 0.125±0.003 (exp) ± 0.008 (theor). The first error is the experimental uncertainty. The second error is due to hadronization uncertainties and approximations in the calculations of the higher order corrections.

3 data tables
Table 1

Measured EEC distribution corrected for detector effects and photon radiation. Errors are combined statistical and systematic uncertainties.

Table 2

Measured average jet multiplicities for the K_PT algorithm. All numbers are corrected for detector effects and photon radiation. Errors are combined statistical and systematic uncertainties.

Table 3

Value of strong coupling constant, alpha_s, determined from the data. First error is experimental, the second is theoretical.


rivet Analysis
Measurement of the inclusive production of neutral pions and charged particles on the Z0 resonance

The L3 collaboration Adeva, B. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 259 (1991) 199-208, 1991.
Inspire Record 314407 DOI 10.17182/hepdata.29468

We present a study of the inclusive production of neutral pions and charged particles from 112 000 hadronic Z 0 decays. The measured inclusive momentum distributions can be reproduced by parton shower Monte Carlo programs and also by an analytical QCD calculation. Comparing our results to e + e − data between √ s = 9 and 91 GeV, we findfind that the evolution of the spectra with center of mass energy is consistent with the QCD predictions.

6 data tables
Table 1

No description provided.

Table 2

Error is dominated by systematic uncertainties.

Table 3

No description provided.

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HADRON MULTIPLICITY VARIATION WITH Q**2 AND SCALE BREAKING OF THE HADRON DISTRIBUTIONS IN DEEP INELASTIC MUON - PROTON SCATTERING

The European Muon collaboration Arneodo, M. ; Arvidson, A. ; Aubert, J.J. ; et al.
Phys.Lett.B 165 (1985) 222-228, 1985.
Inspire Record 217810 DOI 10.17182/hepdata.30328

Measurements are presented of the variation with Q 2 (scaling violation) of the hadron multiplicity in deep inelastic muon-proton scattering. An increase in the average multiplicity of both the charged hadrons and K 0 mesons is observed with increasing Q 2 or x Bj for fixed centre-of-mass energy W . The study of the shape of the effective fragmentation function D h ( z , W , Q 2 ) shows that the increase of the particle yield with Q 2 takes place for low z particles. The variation of the hadron distributions with Q 2 is also studied in the current fragmentation region where a decrease in multiplicity is observed. Such effects are expected from QCD.

2 data tables
Table 1

No description provided.

Table 2

No description provided.


Studies of Quark and Diquark Fragmentation Into Identified Hadrons in Deep Inelastic Muon - Proton Scattering

The European Muon collaboration Arneodo, M. ; Arvidson, A. ; Aubert, J.J. ; et al.
Phys.Lett.B 150 (1985) 458, 1985.
Inspire Record 206297 DOI 10.17182/hepdata.30438

None

19 data tables
Table 1

Backward Multiplicity.

Table 2

Forward Multiplicity.

Table 3

No description provided.

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