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

1-THRUST distribution.

THRUST-MAJOR distribution.

THRUST-MINOR distribution.

More…

QCD studies and determination of alpha(s) in e+ e- collisions at s**(1/2) = 161-GeV and 172-GeV.

The L3 collaboration Acciarri, M. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 404 (1997) 390-402, 1997.
Inspire Record 443563 DOI 10.17182/hepdata.47483

We present a study of the structure of hadronic events recorded by the L3 detector at LEP at the center of mass energies of 161 and 172 GeV. The data sample corresponds to an integrated luminosity of 21.25 pb −1 collected during the high energy runs of 1996. The distributions of event shape variables 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 at the two energies. Combining this with our earlier measurements we find that the strong coupling constant decreases with increasing energy as expected in QCD.

8 data tables

No description provided.

Average jet multiplicity using JADE algorithm.

Average jet multiplicity using Durham algorithm.

More…

Measurement of event shape and inclusive distributions at s**(1/2) = 130-GeV and 136-GeV.

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.
Z.Phys.C 73 (1997) 229-242, 1997.
Inspire Record 424629 DOI 10.17182/hepdata.47715

Inclusive charged particle and event shape distributions are measured using 321 hadronic events collected with the DELPHI experiment at LEP at effective centre of mass energies of 130 to 136 GeV. These distributions are presented and compared to data at lower energies, in particular to the precise Z data. Fragmentation models describe the observed changes of the distributions well. The energy dependence of the means of the event shape variables can also be described using second order QCD plus power terms. A method independent of fragmentation model corrections is used to determine αs from the energy dependence of the mean thrust and heavy jet mass. It is measured to be: $$←pha _s(133 {⤪ GeV})={0.116}pm {0.007}_{exp-0.004theo}^{+0.005}$$ from the high energy data.

26 data tables

mean values for event shape variables.

Integral of event shape distribution over the specified interval.

Integral of event shape distribution over the specified interval.

More…

Measurement of eta production in two and three jet events from hadronic Z decays at LEP

The L3 collaboration Acciarri, M. ; Adam, A. ; Adriani, O. ; et al.
Phys.Lett.B 371 (1996) 126-136, 1996.
Inspire Record 404602 DOI 10.17182/hepdata.48038

The inclusive production of η mesons has been studied using 1.6 million hadronic Z decays collected with the L3 detector. The η multiplicity per event, the multiplicity for two-jet and three-jet events separately, and the multiplicity in each jet have been measured and compared with the predictions of different Monte Carlo programs. The momentum spectra of η in each jet have also been measured. We observe that the measured η momentum spectrum in quark-enriched jets agrees well with the Monte Carlo prediction while in gluon-enriched jets it is harder than that predicted by the Monte Carlo models.

6 data tables

No description provided.

No description provided.

No description provided.

More…

Test of the flavor independence of alpha-s

The ALEPH collaboration Buskulic, D. ; Casper, D. ; De Bonis, I. ; et al.
Phys.Lett.B 355 (1995) 381-393, 1995.
Inspire Record 393416 DOI 10.17182/hepdata.48177

Using about 950000 hadronic events collected during 1991 and 1992 with the ALEPH detector, the ratios r b = α s b α s udsc and r uds = α s uds α s cb have been measured in order to test the flavour independence of the strong coupling constant α s . The analysis is based on event-shape variables using the full hadronic sample, two b -quark samples enriched by lepton tagging and lifetime tagging, and a light-quark sample enriched by lifetime antitagging. The combined results are r b = 1.002±0.023 and r uds = 0.971 ± 0.023.

1 data table

No description provided.


Determination of alpha-s using the next-to-leading log approximation of QCD

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adye, T. ; et al.
Z.Phys.C 59 (1993) 21-34, 1993.
Inspire Record 354909 DOI 10.17182/hepdata.50115

A new measurement of αs is obtained from the distributions in thrust, heavy jet mass, energy-energy correlation and two recently introduced jet broadening variables following a method proposed by Cata

7 data tables

Thrust distribution corrected for detector acceptance and initial state photon radiation.

Heavy jet mass (RHO) distribution (THRUST definition) corrected for detect or acceptance and initial state photon radiation.

Heavy jet mass (RHOM) distribution (MASS definition) corrected for detectoracceptance and initial state photon radiation.

More…

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

Sphericity distribution.

Sphericity distribution.

Aplanarity distribution.

More…

Measurement of alpha-s in hadronic Z decays using all orders resummed predictions

The ALEPH collaboration Decamp, D. ; Deschizeaux, B. ; Goy, C. ; et al.
Phys.Lett.B 284 (1992) 163-176, 1992.
Inspire Record 333334 DOI 10.17182/hepdata.48421

None

1 data table

Three different methods are used for extraction Alphas value (see text for details). Systematical errors with C=HADR and C=THEOR are due to hadronization correction and theoretical uncertainties.


Measurement of the strong coupling constant alpha-s from global event shape variables of hadronic Z decays

The ALEPH collaboration Decamp, D. ; Deschizeaux, B. ; Goy, C. ; et al.
Phys.Lett.B 255 (1991) 623-633, 1991.
Inspire Record 301661 DOI 10.17182/hepdata.29491

An analysis of global event-shape variables has been carried out for the reaction e + e − →Z 0 →hadrons to measure the strong coupling constant α s . This study is based on 52 720 hadronic events obtained in 1989/90 with the ALEPH detector at the LEP collider at energies near the peak of the Z-resonance. In order to determine α s , second order QCD predictions modified by effects of perturbative higher orders and hadronization were fitted to the experimental distributions of event-shape variables. From a detailed analysis of the theoretical uncertainties we find that this approach is best justified for the differential two-jet rate, from which we obtain α s ( M Z 2 ) = 0.121 ± 0.002(stat.)±0.003(sys.)±0.007(theor.) using a renormalization scale ω = 1 2 M Z . The dependence of α s ( M Z 2 ) on ω is parameterized. For scales m b <ω< M Z the result varies by −0.012 +0.007 .

1 data table

The second DSYS error is the theoretical error.


A Comparison of jet production rates on the Z0 resonance to perturbative QCD

The DELPHI collaboration Abreu, P. ; Adam, W. ; Adami, F. ; et al.
Phys.Lett.B 247 (1990) 167-176, 1990.
Inspire Record 297698 DOI 10.17182/hepdata.29653

The production rates for 2-, 3-, 4- and 5-jet hadronic final states have been measured with the DELPHI detector at the e + e − storage ring LEP at centre of mass energies around 91.5 GeV. Fully corrected data are compared to O(α 2 s ) QCD matrix element calculations and the QCD scale parameter Λ MS is determined for different parametrizations of the renormalization scale ω 2 . Including all uncertainties our result is α s ( M 2 Z )=0.114±0.003[stat.]±0.004[syst.]±0.012[theor.].

2 data tables

Corrected jet rates.

Second systematic error is theoretical.