Measurement of $\Z^0$ Decays to Hadrons and a Precise Determination of the Number of Neutrino Species

The L3 collaboration Adeva, B. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 237 (1990) 136-146, 1990.
Inspire Record 286423 DOI 10.17182/hepdata.29736

We have made a precise measurement of the cross section for e + e − →Z 0 →hadrons with the L3 detector at LEP, covering the s range from 88.28 to 95.04 GeV. From a fit to the Z 0 mass, total width, and the hadronic cross section to be M Z 0 =91.160 ± 0.024 (experiment) ±0.030(LEP) GeV, Γ Z 0 =2.539±0.054 GeV, and σ h ( M Z 0 )=29.5±0.7 nb. We also used the fit to the Z 0 peak cross section and the width todetermine Γ invisible =0.548±0.029 GeV, which corresponds to 3.29±0.17 species of light neutrinos. The possibility of four or more neutrino flavors is thus ruled out at the 4σ confidence level.

2 data tables

No description provided.

Total hadronic cross section.


A Determination of the Properties of the Neutral Intermediate Vector Boson Z0

The L3 collaboration Adeva, B. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 231 (1989) 509, 1989.
Inspire Record 282041 DOI 10.17182/hepdata.29768

We report the results of first physics runs of the L3 detector at LEP. Based on 2538 hadron events, we determined the mass m z 0 and the width Γ z 0 of the intermediate vector boson Z 0 to be m z 0 =91.132±0.057 GeV (not including the 46 MeV LEP machine energy uncertainty) and Γ z 0 =2.588±0.137 GeV. We also determined Γ invisible =0.567±0.080 GeV, corresponding to 3.42±0.48 number of neutrino flavors. We also measured the muon pair cross section and determined the branching ratio Γ μμ = Γ h =0.056±0.006. The partial width of Z 0 →e + e − is Γ ee =88±9±7 MeV.

1 data table

No description provided.


Measurement of $g$(a) and $g(V$), the Neutral Current Coupling Constants to Leptons

The L3 collaboration Adeva, B. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 236 (1990) 109-115, 1990.
Inspire Record 283470 DOI 10.17182/hepdata.29715

We have measured both the rates and the forward-backward asymmetry of ℓ + ℓ − from Z 0 →ℓ + ℓ − (where ℓ= μ , τ ) with the L3 detector. We obtained Γ ℓℓ =88±4±3 MeV and the vector neutral current coupling constant, g v =0.00±0.07 and the axial vector neutral current coupling constant, g A =−0.515±0.015.

2 data tables

No description provided.

No description provided.


Decay properties of tau leptons measured at the Z0 resonance

The L3 collaboration Adeva, B. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 265 (1991) 451-461, 1991.
Inspire Record 318230 DOI 10.17182/hepdata.40873

From 2540 Z 0 → τ + τ − events, we determine the inclusive decay branching fractions of the τ -lepton into one and three charged particles to be 0.856 ± 0.006 (stat.) ± 0.003 (syst.) and 0.144 ± 0.006 (stat.) ± 0.003 (syst.), respectively. The leptonic branching fractions are measured to be 0.175 ± 0.008 (stat.) ± 0.005 (syst.) for τ → μν μ ντ and 0.177 ± 0.007 (stat.) ± 0.006 (syst.) for τ → eν e ν τ . We determined the τ lifetime both from three-prong decays using the decay length and from one-prong decays using the impact parameter. The results from the two independent methods agree and yield a combined value of [0.309 ± 0.023 (stat.) ± 0.030 (syst.)] × 10 −12 s.

1 data table

ALPHAS extracted from the ratio of the branching fractions.


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

No description provided.

Error is dominated by systematic uncertainties.

No description provided.

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A Test of quantum electrodynamics in the reaction e+ e- ---> gamma gamma (gamma)

The L3 collaboration Adriani, O. ; Aguilar-Benitez, M. ; Ahlen, S. ; et al.
Phys.Lett.B 288 (1992) 404-411, 1992.
Inspire Record 336900 DOI 10.17182/hepdata.29221

We have measured the total and differential cross sections of the reaction e + e − → γγ ( γ ) at center-of-mass energies around 91 GeV, with an integrated luminosity of 14.2 pb −1 . The results are in good agreement with QED predictions. We set lower limits, at 95% confidence level, on the QED cutoff parameters of Λ + > 139 GeV, Λ − > 108 GeV and on the mass of an excited electron of m e∗ > 127 GeV . We searched for Z 0 rare decays with photonic signitures in the final state. Upper limits, at 95% confidence level, for branching ratio of Z 0 decaying into π 0 γ / γγ , νγ and γγγ are 1.2 × 10 −4 , 1.8 × 10 −4 , 3.3 × 10 −5 respectively.

3 data tables

Measured cross section for the 1991 data.

Measured cross section for the 1990 data.

Measured differential cross sections of combined 1990 and 1991 data.


Measurement of the e+ e- --> b anti-b and e+ e- --> c anti-c forward backward asymmetries at the Z0 resonance

The L3 collaboration Adriani, O. ; Aguilar-Benitez, M. ; Ahlen, S. ; et al.
Phys.Lett.B 292 (1992) 454-462, 1992.
Inspire Record 339089 DOI 10.17182/hepdata.29017

We have measured the forward-backward asymmetry in e + e − → b b and e + e − → c c processes using hadronic events containing muons or electrons. The data sample corresponds to 4100000 hadronic decays of the Z 0 . From a fit to the single lepton and dilepton p and p T spectra, we determine A b b =0.086±0.015±0.007 and A c c =0.083±0.038±0.027 at the effective center-of-mass energy √ s =91.24 GeV. These measurements yield a value of the electroweak mixing angle sin 2 θ w =0.2336±0.0029 .

4 data tables

No description provided.

No description provided.

No description provided.

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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

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

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.

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


Determination of the number of light neutrino species

The L3 collaboration Adriani, O. ; Aguilar-Benitez, M. ; Ahlen, S. ; et al.
Phys.Lett.B 292 (1992) 463-471, 1992.
Inspire Record 339090 DOI 10.17182/hepdata.29030

We have measured the cross-section of the production of single photon events in e + e − collisions near the Z 0 resonance. For an integrated luminosity of 9.6 pb −1 , we have observed 202 single photon candidates with energy between 0.9 and 3.5 GeV in the polar angular region between 45° and 135°. Assuming that the only stable weakly interacting particles are light neutrinos with standard model couplings, we determine the number of light neutrino species to be N v = 3.14 ± 0.24 (stat.)±0.12 (syst.). This corresponds to an invisible Z 0 width of Γ inv = 524 ± 40 ± 20 MeV.

1 data table

Corrected cross section.


Measurement of inclusive eta production in hadronic decays of the Z0

The L3 collaboration Adriani, O. ; Aguilar-Benitez, M. ; Ahlen, S. ; et al.
Phys.Lett.B 286 (1992) 403-412, 1992.
Inspire Record 336180 DOI 10.17182/hepdata.29161

We present a study of the inclusive η production based on 300 000 hadronic Z 0 decays. The measured inclusive momentum distribution can be reproduced by parton shower Monte Carlo programs and also by an analytical QCD calculation. Comparing our results with low energy e + e − data, we find that QCD describes both the shape and the energy evolution of the η spectrum. The comparison of η production rates in quark- and gluon-enriched jet samples does not show statistically significant evidence for more abundant production of η mesons in gluon fragmentation.

2 data tables

Differential cross section for inclusive eta production, normalized to the total hadronic cross section.

Differential cross section for inclusive eta production, normalized to the total hadronic cross section.