0000000000915841

AUTHOR

A Gamess

showing 7 related works from this author

Measurement of electroweak parameters from Z decays into fermion pairs

1990

We report on the properties of theZ resonance from 62 500Z decays into fermion pairs collected with the ALEPH detector at LEP, the Large Electron-Positron storage ring at CERN. We findMZ=(91.193±0.016exp±0.030LEP) GeV, ΓZ=(2497±31) MeV, σhad0=(41.86±0.66)nb, and for the partial widths Γinv=(489±24) MeV, Γhad(1754±27) MeV, Γee=(85.0±1.6)MeV, Γμμ=(80.0±2.5) MeV, and Γττ=(81.3±2.5) MeV, all in good agreement with the Standard Model. Assuming lepton universality and using a lepton sample without distinction of the final state we measure Γu=(84.3±1.3) MeV. The forward-backward asymmetry in leptonic decays is used to determine the vector and axial-vector weak coupling constants of leptors,gv2(MZ2…

PhysicsCoupling constantParticle physicsPhysics and Astronomy (miscellaneous)media_common.quotation_subjectElectron–positron annihilationElectroweak interactionWeinberg angleFermionAsymmetryNuclear physicsHigh Energy Physics::ExperimentNeutrinoNuclear ExperimentEngineering (miscellaneous)Particle Physics - ExperimentLeptonmedia_common
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A Study of Bose-Einstein Correlations In e+e- Annihilation At 91 Gev

1992

This paper describes a study of Bose-Einstein correlations made using the ALEPH detector at LEP. The correlations are found to enhance the two particle differential cross section for pairs of identical pions by a factor which can be roughly parametrized by R(Q) = 1 + lambda exp(-Q2-sigma(2)), where Q is the difference in the 3-momenta of the two pions in their centre of mass frame, lambda = 0.51 +/- 0.04 +/- 0.11 and sigma = 3.3 +/- 0.2 +/- 0.8 GeV-1, which corresponds to a source size of 0.65 +/- 0.04 +/- 0.16 fm. The large systematic errors on these results reflect their strong dependence on the choice of the reference sample used in the analysis. This problem is believed to occur primari…

PhysicsParticle physicsAnnihilationPhysics and Astronomy (miscellaneous)Electron–positron annihilationStrong interactionElementary particleBose–Einstein correlationsLEPResonance (particle physics)Nuclear physicsPionMONTE-CARLOCOHERENCEPARTICLESHigh Energy Physics::ExperimentQuantum field theoryNuclear ExperimentEngineering (miscellaneous)Particle Physics - ExperimentMULTIPLE PRODUCTION
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Search for a very light CP-odd neutral Higgs boson of the MSSM

1992

Abstract The reactions e + e − → hZ ∗ and e + e − → hA have been used to search for the neutral Higgs bosons h and A of the MSSM in the case where the CP -odd A is lighter than 2 m μ , taking into account the large h → AA decay branching ratio. No signal was found in the data sample collected until the end of 1991 by the ALEPH experiment at LEP. For tan β ⩾, m A m μ is excluded at 95% CL for any m h .

PhysicsNuclear physicsNuclear and High Energy PhysicsParticle physicsBranching fractionHiggs bosonLEPALEPH experimentParticle Physics - ExperimentBoson
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Measurement of charge asymmetry in hadronic Z decays

1991

A significant charge asymmetry is observed in the hadronic Z decays with the ALEPH detector at LEP. The asymmetry expressed in terms of the difference in momentum weighted charges in the two event hemispheres is measured to be − = −0.0084±0.0015 (stat.) ±0.0004 (exp. sys.). In the framework of the standard model this can be interpreted as a measurement of the effective electroweak mixing angle, sin2Ow (Mz2=0.2300±0.0034 (stat.) ±0.0010 (exp. sys.) ±0.0038 (theor. sys.) or of the ratio of the vector to axual- vector coupling costants of the electron, gvegAe=+0.073±0.024.

PhysicsNuclear and High Energy PhysicsParticle physicsmedia_common.quotation_subjectElectron–positron annihilationElectroweak interactionHadronWeinberg angleCharge (physics)AsymmetryStandard ModelNuclear physicsMomentumHigh Energy Physics::ExperimentNuclear ExperimentParticle Physics - Experimentmedia_common
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MEASUREMENT OF TAU BRANCHING RATIOS

1992

著者人数：112名

PhysicsParticle physicsPhysics and Astronomy (miscellaneous)Branching fractionElectron–positron annihilationLEPTON PRODUCTIONPIONSHadronEconomic intelligenceCELLO DETECTORBranching (polymer chemistry)Charged particlePARAMETERSNuclear physicsPionPETRAHigh Energy Physics::ExperimentEngineering (miscellaneous)Particle Physics - ExperimentLeptonDECAY MODES
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Measurement of α from the structure of particle clusters produced in hadronic Z decays

1991

Abstract Using 106 000 hadronic events obtained with the ALEPH detector at LEP at energies close to the Z resonance peak, the strong coupling constant αs is measured by an analysis of energy-energy correlations (EEC) and the global event shape variables thrust, C-parameter and oblateness. It is shown that the theoretical uncertainties can be significantly reduced if the final state particles are first combined in clusters using a minimum scaled invariant mass cut, Ycut, before these variables are computed. The combined result from all shape variables of pre-clustered events is αs(MZ2 = 0.117±0.005 for a renormalization scale μ= 1 2 M Z . For μ values between MZ and the b-quark mass, the res…

PhysicsNuclear and High Energy PhysicsParticle physicsmedia_common.quotation_subjectElectron–positron annihilationHadronAsymmetryResonance (particle physics)RenormalizationNuclear physicsParticleHigh Energy Physics::ExperimentInvariant massEvent (particle physics)Particle Physics - Experimentmedia_commonPhysics Letters B
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Measurement of the charged particle multiplicity distribution in hadronic Z decays

1991

The charged particle multiplicity distribution of hadronic Z decays was measured on the peak of the Z resonance using the ALEPH detector at LEP. Using a model independent unfolding procedure the distribution was found to have a mean = 20.85 +/- 0.24 and a dispersion D = 6.34 +/- 0.12. Comparison with lower energy data supports the KNO scaling hypothesis in the energy range square-root s = 29-91.25 GeV. At square-root s = 91.25 GeV the shape of the multiplicity distribution is well described by a log-normal distribution, as predicted from a cascading model for multi-particle production. The same model also successfully describes the energy dependence of the mean and width of the multiplicity…

Quantum chromodynamicsPhysicsNuclear and High Energy PhysicsRange (particle radiation)Particle physicsE+E ANNIHILATIONPP COLLISIONSDistribution (number theory)Electron–positron annihilationQUARKHadronPETRA ENERGIESResonance (particle physics)Charged particleNuclear physicsMONTE-CARLOHigh Energy Physics::ExperimentFRAGMENTATIONScalingParticle Physics - Experiment
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