Studies of hadronic event structure in e+ e- annihilation from 30-GeV to 209-GeV with the L3 detector

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Rept. 399 (2004) 71-174, 2004.
Inspire Record 652683 DOI 10.17182/hepdata.54900

In this Report, QCD results obtained from a study of hadronic event structure in high energy e^+e^- interactions with the L3 detector are presented. The operation of the LEP collider at many different collision energies from 91 GeV to 209 GeV offers a unique opportunity to test QCD by measuring the energy dependence of different observables. The main results concern the measurement of the strong coupling constant, \alpha_s, from hadronic event shapes and the study of effects of soft gluon coherence through charged particle multiplicity and momentum distributions.

68 data tables

Jet fractions using the JADE algorithm as a function of the jet resolution parameter YCUT at c.m. energy 130.1 GeV.

Jet fractions using the JADE algorithm as a function of the jet resolution parameter YCUT at c.m. energy 136.1 GeV.

Jet fractions using the JADE algorithm as a function of the jet resolution parameter YCUT at c.m. energy 161.3 GeV.

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QCD studies in e+ e- annihilation from 30-GeV to 189-GeV

The L3 collaboration Acciarri, M. ; Achard, P. ; Adriani, O. ; et al.
Phys.Lett.B 489 (2000) 65-80, 2000.
Inspire Record 527988 DOI 10.17182/hepdata.21126

We present results obtained from a study of the structure of hadronic events recorded by the L3 detector at various centre-of-mass energies. The distributions of event shape variables and the energy dependence of their mean values are measured from 30GeV to 189GeV and compared with various QCD models. The energy dependence of the moments of event shape variables is used to test a power law ansatz for the non-perturbative component. We obtain a universal value of the non-perturbative parameter alpha_0 = 0.537 +/- 0.073. From a comparison with resummed O(alpha_s^2) QCD calculations, we determine the strong coupling constant at each of the selected energies. The measurements demonstrate the running of alpha_s as expected in QCD with a value of alpha_s(m_Z) = 0.1215 +/- 0.0012 (exp) +/- 0.0061 (th).

22 data tables

Distribution for THRUST at c.m. energy 189 GeV.

Distribution for Heavy Jet Mass at c.m. energy 189 GeV.

Distribution for Total Jet Broadening at c.m. energy 189 GeV.

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Inclusive production of pi0, eta, eta'(958), K0(S) and Lambda in two- and three-jet events from hadronic Z decays.

The ALEPH collaboration Barate, R. ; Decamp, D. ; Ghez, Philippe ; et al.
Eur.Phys.J.C 16 (2000) 613, 2000.
Inspire Record 507531 DOI 10.17182/hepdata.49106

The production rates and the inclusive cross sections of the isovector meson${\rm \pi^0}$, the isoscalar mesons$\eta$and

25 data tables

Inclusive cross section for PI0 production in hadronic events.

Inclusive cross section for ETA production in hadronic events.

Inclusive cross section for ETAPRIME production in hadronic events.

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Measurement of the jet width in gamma gamma collisions and in e+ e- annihilation process at TRISTAN

The TOPAZ collaboration Adachi, K. ; Hayashii, H. ; Miyabayashi, K. ; et al.
Phys.Lett.B 451 (1999) 256-266, 1999.
Inspire Record 494502 DOI 10.17182/hepdata.43768

The shape of jets produced in (quasi-) real photon-photon collisions as well as in e^+e^- annihilation process has been studied with a cone jet finding algorithm, using the data taken with the TOPAZ detector at the TRISTAN e^+e^- collider at an average center-of-mass energy of 58 GeV. The results are presented in terms of the jet width as a function of the jet transverse energy(E^{jet}_T) as well as a scaled transverse jet energy, x_T(=2E^{jet}_T/root(s)). The jet width narrows as E^{jet}_T increases; however, at the same value of E^{jet}_T the jet width in gamma-gamma collisions at TRISTAN is significantly narrower than that in gamma p collisions at HERA. By comparing our results with the data in other reactions, it has been shown that the jet width in gamma-gamma, gamma p, p\bar{p} collisions as well as the e^+e^- annihilation process has an approximate scaling behavior as a function of x_T.

2 data tables

The jet width is defined as the full width at the half maximum of the distribution of the transverse energy flow.

The jet width is defined as the full width at the half maximum of the distribution of the transverse energy flow.


QCD results from studies of hadronic events produced in e+ e- annihilations at s**(1/2) = 183-GeV.

The L3 collaboration Acciarri, M. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 444 (1998) 569-582, 1998.
Inspire Record 477808 DOI 10.17182/hepdata.49364

We present results obtained from a study of the structure of hadronic events recorded by the L3 detector at a centre-of-mass energy of 183 GeV. The data sample corresponds to an integrated luminosity of 55.3 pb −1 . The distributions of event shape variables and the energy dependence of their mean values are measured. From a comparison with resummed O ( α s 2 ) QCD calculations, we determine the strong coupling constant α s (183 GeV )=0.1086 ± 0.0026 (exp) ± 0.0054 (th) . The charged particle multiplicity distribution and momentum spectrum are studied and the energy dependence of the peak position of the ξ (=−ln x p ) distribution is compared with lower energy measurements and QCD expectations.

1 data table

These data are superceded by the analysis presented in Acciarri et al PL B489,65.


A study of parton fragmentation in hadronic Z0 decays using Lambda Antilambda correlations.

The OPAL collaboration Abbiendi, G. ; Ackerstaff, K. ; Alexander, G. ; et al.
Eur.Phys.J.C 13 (2000) 185-195, 2000.
Inspire Record 474010 DOI 10.17182/hepdata.49312

The correlated production of Lambda and Lambdabar baryons has been studied using 4.3 million multihadronic Zo decays recorded with the OPAL detector at LEP. Di-lambda pairs were investigated in the full data sample and for the first time also in 2-jet and 3-jet events selected with the k_t algorithm. The distributions of rapidity differences from correlated Lambda-Lambdabar pairs exhibit short-range, local correlations and prove to be a sensitive tool to test models, particularly for 2-jet events. The JETSET model describes the data best but some extra parameter tuning is needed to improve agreement with the experimental results in the rates and the rapidity spectra simultaneously. The recently developed modification of JETSET, the MOdified Popcorn Scenarium (MOPS), and also HERWIG do not give satisfactory results. This study of di-lambda production in 2- and 3-jet events supports the short-range compensation of quantum numbers.

5 data tables

Average multipicity of LAMBDA pairs in hadronic events.

Average multipicity of LAMBDA pairs in 2-Jet events.

Average multipicity of LAMBDA pairs in 3-Jet events.

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Study of the structure of hadronic events and determination of alpha-s at s**(1/2) = 130-GeV and 136-GeV

The L3 collaboration Acciarri, M. ; Adam, A. ; Adriani, O. ; et al.
Phys.Lett.B 371 (1996) 137-148, 1996.
Inspire Record 404916 DOI 10.17182/hepdata.48010

We present a study of the structure of hadronic events recorded by the L3 detector at center-of-mass energies of 130 and 136 GeV. The data sample corresponds to an integrated luminosity of 5 pb −1 collected during the high energy run of 1995. The shapes of the event shape distributions and the energy dependence of their mean values are well reproduced by QCD models. From a comparison of the data with resummed O (α s 2 ) QCD calculations, we determine the strong coupling constant to be α s (133 GeV) = 0.107 ± 0.005(exp) ± 0.006(theor).

3 data tables

Mean values of the event shape variables.

Mean charged particle multiplicity.

The value of alpha_s from the fits to the event shape variables : thrust (THRUST), scale heavy jet mass (MH**2/S), total jet broadening (BT)and wide jet broadening (BW). The last value is combined result (COMBINED). The second systematic error is due to uncertainties in the theory.


A Determination of alpha-s in e+ e- annihilation at s**(1/2) = 57.3-GeV

The AMY collaboration Li, Y.K. ; Sagawa, H. ; Bodek, A. ; et al.
Phys.Lett.B 355 (1995) 394-400, 1995.
Inspire Record 406129 DOI 10.17182/hepdata.6546

We present a study of differential two jet ratios in multi-hadronic final states produced by e + e − annihilation in the AMY detector at TRISTAN. The data are compared to the predictions of the next-to-leading logarithm parton-shower (NLL PS) Monte Carlo and the O ( α s 2 ) matrix element QCD models. We determine the strong coupling strength α s (57.3 GeV) = 0.130 ± 0.006.

6 data tables

The data are compared to the predictions of Monte-Carlo.

Using the p-scheme for jet clustering.

Using the E-scheme for jet clustering.

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A Study of mean subjet multiplicities in two and three jet hadronic Z0 decays

The OPAL collaboration Akers, R. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 63 (1994) 363-376, 1994.
Inspire Record 372997 DOI 10.17182/hepdata.48236

This paper describes an analysis of sub-jet multiplicities, which are expected to be sensitive to the properties of soft gluon radiation, in hadronic decays of theZ0. Two- and three-jet event samples are selected using thek⊥ jet clustering algorithm at a jet resolution scaley1. The mean sub-jet multiplicity as a function of the sub-jet resolution,y0, is determined separately for both event samples by reapplying the same jet algorithm at resolution scalesy0<y1. These measurements are compared with recent perturbative QCD calculations based on the summation of leading and next-to-leading logarithms, and with QCD Monte Carlo models. The analytic calculations provide a good description of the sub-jet multiplicity seen in three- and two-jet mvents in the perturbative region (y0≈y1)), and the measured form of the data is in agreement with the expectation based on coherence of soft gluon radiation. The analysis provides good discrimination between Monte Carlo models, and those with a coherent parton shower are preferred by the data. The analysis suggests that coherence effects are present in the data.

4 data tables

Ratio of multiplicities of sub-jets from 3 and 2 jet samples. Data are corrected to the hadron level and have combined statistical and systematic errors.

Sub-jet multiplicity for 3 jet sample. Data corrected to the hadron level and have combined statistical and systematic errors.

Sub-jet multiplicity for 2 jet sample. Data corrected to the hadron level and have combined statistical and systematic errors.

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QCD studies using a cone based jet finding algorithm for e+ e- collisions at LEP

The OPAL collaboration Akers, R. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 63 (1994) 197-212, 1994.
Inspire Record 373000 DOI 10.17182/hepdata.48238

We describe a cone-based jet finding algorithm (similar to that used in\(\bar p\)p experiments), which we have applied to hadronic events recorded using the OPAL detector at LEP. Comparisons are made between jets defined with the cone algorithm and jets found by the “JADE” and “Durham” jet finders usually used ine+e− experiments. Measured jet rates, as a function of the cone size and as a function of the minimum jet energy, have been compared with O(αs2) calculations, from which two complementary measurements\(\alpha _s \left( {M_{Z^0 } } \right)\) have been made. The results are\(\alpha _s \left( {M_{Z^0 } } \right)\)=0.116±0.008 and\(\alpha _s \left( {M_{Z^0 } } \right)\)=0.119±0.008 respectively, where the errors include both experimental and theoretical uncertainties. Measurements are presented of the energy flow inside jets defined using the cone algorithm, and compared with equivalent data from\(\bar p\)p interactions, reported by the CDF collaboration. We find that the jets ine+e− are significantly narrower than those observed in\(\bar p\)p. The main contribution to this effect appears to arise from differences between quark- and gluon-induced jets.

16 data tables

Measured 2 jet production rate as a function of EPSILON, the minimum energy of a jet for a fixed cone radius R = 0.7 radians.

Measured 2 jet production rate as a function of R, the jet cone radius, for a fixed value of the minimum jet energy, EPSILON, of 7 GeV.

Measured 3 jet production rate as a function of EPSILON, the minimum energy of a jet for a fixed cone radius R = 0.7 radians.

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