Lifetime and Production Rate of Beauty Baryons from Z Decays

The production and decay of beauty baryons (b-baryons) have been studied using 1.7×106 Z hadronic decays collected by the DELPHI detector at LEP. Three different techniques were used to identify the b-baryons. The first method used pairs of a Λ and a lepton to tag the b-baryon decay. The second method associated fully reconstructed ΛC baryons with leptons. The third analysis reconstructed the b-baryon decay points by forming secondary vertices from identified protons and muons of opposite sign. Using these methods the following production rates were measured:[Figure not available: see fulltext.] The average b-baryon lifetime was determined to be:[Figure not available: see fulltext.] © 1995 Springer-Verlag0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Study of Prompt Photon Production in Hadronic Z0 Decays

From a sample of 1.5 million Z0→qq decays collected by the DELPHI detector during 1991, 1992 and 1993, the production cross section for isolated final state photons is measured and is compared with the O(α, αs) matrix element calculations implemented in the EEPRAD and GNJETS Monte Carlo generators. The observed photon yield is used to derive the electroweak couplings of charge 2/3 (u-type) and charge 1/3 (d-type) quarks to the Z0 boson. The measured values c2/3=0.91-0.36 +0.25 and c1/3=1.62-0.17 +0.24 are compatible with the Standard Model prediction, c2/3=1.145 and c1/3=1.477. © 1996 Springer-Verlag.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Measurement of Time Dependent Bd0- Bd0- Mixing

The time dependent mixing of Bd 0-B̄d 0 mesons has been observed by using the correlations between the charge of D* mesons and the weighted mean charge of particles in each hemisphere. From a reconstructed D*± sample corresponding to about 1.7 million hadronic Z0 decays, the mass difference between the two Bd 0 mass eigenstates has been measured to be Δm = 0.50±0.12 (stat.) ± 0.06 (syst.) (Latin small letter h with stroke sign)/ps or, converting into eV/c2: Δm = [3.29±0.79 (stat.) ± 0.39 (syst.)] 10-4 eV/c2.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Study of Hadronic Decays of the Z0 Boson

Hadronic decays of Z0 bosons are studied in the Delphi detector. Global event variables and single particle inclusive distributions are compared with QCD-based predictions. The mean charged multiplicity is found to be 20.6±1.0 (stat+syst). The mean values of the sphericity, aplanarity, thrust, minor value, pin T and pout T are compared with values found at lower energy e+e- colliders.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

A Search for Sleptons and Gauginos in Z0 Decays

Using a data sample corresponding to 10 000 hadronic Z0 decays, we have searched for the production of sleptons and gauginos in the two-prong decays of Z0. No candidate remains after straightforward selections. For neutralinos, we use selection methods developed in our previous search for neutral Higgs particles. The negative results are translated into improved mass limits and parameter constraints on the minimal supersymmetric extension of the standard model.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

A Study of the Decays of Tau Leptons produced on the Z Resonance at LEP

From the analysis of a data sample corresponding to an integrated luminosity of 4.63 pb-1 taken during the 1990 run of LEP at centre of mass energies between 88.2 GeV an 94.2 GeV, the tau decays {Mathematical expression} and their charge conjugates have been studied. The following branching ratios have been measured; {Mathematical expression}, {Mathematical expression}, Br(τ- → π- (K-)vτ)=11.9±0.7±0.7%, BR (τ- → ρ- vτ)= 22.4±0.8±1.3%, in good agreement with world averages. The measured electronic and muonic branching ratios lead to a measurement of the strong coupling constant, αs (mτ) = 0.26-0.12 +0.09. Extrapolating the αs value from mτ to mZ yields αs (mZ) = 0.109-0.028 +0.012. The average polarization Pτ of taus produced in Z → τs τs decays has also been measured using the above decay modes. The weighted mean of the polarizations obtained from the four decay modes is Pτ=-0.24±0.07. This value of Pτ gives, in the improved Born approximation, a ratio between the axial and vector coupling constants of the tau of υτ/aτ = 0.12 ± 0.04, and hence a value of the effective electroweak mixing parameter sin2 θW(mZ 2). © 1992 Springer-Verlag.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Review of Particle Properties, 1970 Jan

This review of the properties of leptons, mesons, and baryons is an updating of Review of Particle Properties, Particle Data Group Rev. Mod. Phys. 41, 109 (1969). Data are evaluated, listed, averaged, and summarized in tables and wallet sheets. A data booklet is also available