Date

Charged hadron multiplicities in e+ e- annihilations at s**(1/2) = 50-GeV - 61.4-GeV

The AMY collaboration Zheng, H.W. ; Perez, P. ; Auchincloss, Priscilla S. ; et al.
Phys.Rev.D 42 (1990) 737-747, 1990.
Inspire Record 295160 DOI 10.17182/hepdata.22922

We present the charged-particle multiplicity distributions for e+e− annihilation at center-of-mass energies from 50 to 61.4 GeV. The results are based on a data sample corresponding to a total integrated luminosity of 30 pb−1 obtained with the AMY detector at the KEK storage ring TRISTAN. The charged-particle multiplicity distributions deviate significantly from the modified Poisson and pair Poisson distributions, but follow Koba-Nielsen-Olesen scaling and are well reproduced by the LUND parton-shower model.

2 data tables

Fully corrected charged particle multiplicity distributions. Errors for n=2 and 4 are systematic only since these were derived using the LUND 6.3 Monte Carlo normalized to the observations at higher n values.

No description provided.


Analysis of Z0 couplings to charged leptons

The OPAL collaboration Akrawy, M.Z. ; Alexander, G. ; Allison, J. ; et al.
Phys.Lett.B 247 (1990) 458-472, 1990.
Inspire Record 297139 DOI 10.17182/hepdata.29630

The couplings of the Z 0 to charged leptons are studied using measurements of the lepton pair cross sections and forward-backward asymmetries at centre of mass energies near to the mass of the Z 0 . The data are consistent with lepton universality. Using a parametrisation of the lepton pair differential cross section which assumes that the Z 0 has only vector and axial couplings to leptons, the charged leptonic partial decay width of the Z 0 is determined to be Г ol+ol− = 83.1±1.9 MeV and the square of the product of the effective axial vector and vector coupling constants of the Z 0 to charged leptons to be a ̌ 2 ol v ̌ 2 ol = 0.0039± 0.0083 , in agreement with the standard model. A parametrisation in the form of the improved Born approximation gives effective leptonic axial vector and vector coupling constants a ̌ 2 ol = 0.998±0.024 and v ̌ 2 ol = 0.0044±0.0083 . In the framework of the standard model, the values of the parameters ϱ z and sin 2 θ w are found to be 0.998±0.024 and 0.233 +0.045 −0.012 respectively. Using the relationship in the minimal standard model between ϱ z and sin 2 θ w , the results sin 2 θ SM w = 0.233 +0.007 −0.006 is obtained. Our previously published measurement of the ratio of the hadronic to the leptonic partial width of the Z 0 is update: R z = 21.72 +0.71 −0.65 .

6 data tables

Cross sections corrected for the effects of efficiency and kinematic cuts. Errors have systematic effects folded.

Acceptance corrected cross sections. Statistical errors only.

Acceptance corrected cross sections. Statistical errors only.

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A Study of coherence of soft gluons in hadron jets

The OPAL collaboration Akrawy, M.Z. ; Alexander, G. ; Allison, J. ; et al.
Phys.Lett.B 247 (1990) 617-628, 1990.
Inspire Record 297564 DOI 10.17182/hepdata.49561

We study the inclusive momentum distribution of charged particles in multihadronic events produced in e + e − annihilations at E CM ∼ M (Z 0 ). We find agreement with the analytical formulae for gluon production that include the phenomena of soft gluon interference. Using data from CM energies between 14 and 91 GeV, we study the dependence of the inclusive momentum distribution on the centre of momentum energy. We find that the analytical formulae describe the data over the entire energy range. Both the momentum distribution at a fixed energy and the change with energy are described by QCD shower Monte Carlo's which include either coherent gluon branchings or string fragmentation. Simple incoherent models with independent fragmentation fail to reproduce the energy dependence and momentum spectra.

1 data table

Statistical errors only. Overall systematic error of 5%.


Experimental study of the axial vector resonances of a1 and h1 in the pi- p charge exchange reaction

Ando, A. ; Imai, K. ; Inaba, S. ; et al.
Phys.Lett.B 291 (1992) 496-502, 1992.
Inspire Record 297738 DOI 10.17182/hepdata.29037

A high-statistics experiment on the reaction π − p→ π + π − π 0 n at 8.06 GeV/ c has been performed using a spectrometer detecting both charged particles and gamma rays. A partial-wave analysis based on the isobar model has been carried out for π + π − π 0 data in the mass range between 0.86 and 1.50 GeV for four t ′ regions: 0.0–0.1, 0.1–0.25, 0.25–0.45 and 0.45–0.95 (GeV/ c 2 ). Two axial-vector resonances, a 1 (1260) and h 1 (1170), were observed in the analysis. The masses and widths of a 1 and h 1 were determined to be M (a 1 = 1121 ± 8 MeV, Λ (a 1 = 239± 11 MeV, M (h 1 = 1168±4 MeV and Λ (h 1 = 345±6 MeV, respectively, by fitting the Breit-Wigner formula to the partial wave amplitude. A fit including the Deck type background was also tried in each t ′ region. The results showed a small effect on these resonance parameters and were consistent with those obtained by the simple Breit-Wigner fitting.

4 data tables

Production cross section of A2(1320) from the 12+ rhoD1+ partial wave.

Production cross section of H1(1190) from the 01+ rhoS0+ partial wave.

Production cross section of A1(1270) from the 11+ rhoS1+ partial wave.

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A Measurement of energy correlations and a determination of alpha-s (M2 (Z0)) in e+ e- annihilations at s**(1/2) = 91-GeV

The OPAL collaboration Akrawy, M.Z. ; Alexander, G. ; Allison, J. ; et al.
Phys.Lett.B 252 (1990) 159-169, 1990.
Inspire Record 298707 DOI 10.17182/hepdata.29525

From an analysis of multi-hadron events from Z 0 decays, values of the strong coupling constant α s ( M 2 Z 0 )=0.131±0.006 (exp)±0.002(theor.) and α s ( M z 0 2 ) = −0.009 +0.007 (exp.) −0.002 +0.006 (theor.) are derived from the energy-energy correlation distribution and its asymmetry, respectively, assuming the QCD renormalization scale μ = M Z 0 . The theoretical error accounts for differences between O ( α 2 s ) calculations. A two parameter fit Λ MS and the renormalization scale μ leads to Λ MS =216±85 MeV and μ 2 s =0.027±0.013 or to α s ( M 2 Z 0 )=0.117 +0.006 −0.008 (exp.) for the energy-energy correlation distribution. The energy-energy correlation asymmetry distribution is insensitive to a scale change: thus the α s value quoted above for this variable includes the theoretical uncertainty associated with the renormalization scale.

3 data tables

Data are at the hadron level, unfolded for initial-state radiation and for detector acceptance and resolution. Note that the systematic errors between bins are correlated.

Alpha-s determined from the EEC measurements. The systematic error is an error in the theory.

Alpha-s determined from the AEEC measurements. The systematic error is an error in the theory.


A Measurement of the photon structure function F2

The AMY collaboration Sasaki, T. ; Yamagishi, Y. ; Tanaka, R. ; et al.
Phys.Lett.B 252 (1990) 491-498, 1990.
Inspire Record 299056 DOI 10.17182/hepdata.29524

The photon structure function F 2 has been measured at average Q 2 values of 73,160 and 390 ( GeV c ) 2 . We compare the x dependence of the Q 2 = 73 ( GeV c ) 2 data with theoretical expectations based on QCD. In addition we present results on the Q 2 evolution of the structure function for the intermediate x range (0.3⩽ x ⩽0.8). The results are consistent with QCD.

4 data tables

X dependence at Q**2 = 73 GeV**2 for light quark data.

X dependence at Q**2 = 73 GeV**2 for total data.

Photon structure function F2 for total data.

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A Study of the recombination scheme dependence of jet production rates and of alpha-s (m(Z0)) in hadronic Z0 decays

The OPAL collaboration Akrawy, M.Z. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 49 (1991) 375-384, 1991.
Inspire Record 299833 DOI 10.17182/hepdata.15085

The error includes the experimental uncertainties (±0.003), uncertainties of hadronisation corrections and of the degree of parton virtualities to which the data are corrected, as well as the uncertainty of choosing the renormalisation scale.

9 data tables

Jet production rates using the E0 recombination scheme.

Jet production rates using the E recombination scheme.

Jet production rates using the p0 recombination scheme.

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The (pi+, K+) reaction on C-12 and Fe-56

Akel, M. ; Amann, J.F. ; Chiba, J. ; et al.
Nucl.Phys.A 534 (1991) 478-492, 1991.
Inspire Record 300837 DOI 10.17182/hepdata.36713

None

2 data tables

Axis error includes +- 0.0/0.0 contribution (?////).

Axis error includes +- 0.0/0.0 contribution (?////).


A measurement of the Z0 invisible width by single photon counting.

The OPAL collaboration Akrawy, M.Z. ; Alexander, G. ; Allison, John ; et al.
Z.Phys.C 50 (1991) 373-384, 1991.
Inspire Record 302586 DOI 10.17182/hepdata.14980

The OPAL detector at LEP is used to measure the branching ratio of theZ0 into invisible particles by measuring the cross section of single photon events ine+e− collisions at centre-of-mass energies near theZ0 resonance. In a data sample of 5.3 pb−1, we observe 73 events with single photons depositing more than 1.5 GeV in the electromagnetic calorimeter, with an expected background of 8±2 events not associated with invisibleZ0 decay. With this data we determine theZ0 invisible width to be 0.50±0.07±0.03 GeV, where the first error is statistical and the second systematic. This corresponds to 3.0±0.4±0.2 light neutrino generations in the Standard Model.

1 data table

No description provided.


Measurement of the cross-sections of the reactions e+ e- ---> gamma gamma and e+ e- ---> gamma gamma gamma at LEP

The OPAL collaboration Akwawy, M.Z. ; Alexander, G. ; Allison, J. ; et al.
Phys.Lett.B 257 (1991) 531-540, 1991.
Inspire Record 302587 DOI 10.17182/hepdata.29464

The cross section of the pure QED process e + e − → γγ has been measured using data accumulated during the 1989 and 1990 scans of the Z 0 resonance at LEP. Both the energy dependence and the angular distribution are in good agreement with the QED prediction. Upper limits on the branching ratios of Z 0 → γγ , Z 0 → π 0 γ and Z 0 → ηγ have been set at 1.4×10 −4 , 1.4×10 −4 and 2.0×10 −4 respectively. Lower limits on the cutoff parameters of the modified electron propagator have been found to be Λ + > 117 GeV and Λ − > 110 GeV. The reaction e + e − → γγγ has also been studied and was found to be consistent with the QED prediction. An upper limit on the branching ratio of Z 0 → γγγ has been set at 6.6 × 10 −5 . All the limits are given at 95% confidence level.

3 data tables

No description provided.

No description provided.

No description provided.