A Measurement of Tau Polarization in Z0 Decays

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A Measurement of Pi-Polarization at Lep

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An improved measurement of B0Bˉ0^{0}\bar{B}^{0} mixing in Z0^0 decays

A more precise determination of the B0-B0 mixing parameter in Z0 decays based on a fourfold increase in statistics has been made using the 1990 and 1991 L3 data. The analysis of the dilepton events, muons and electrons, gives: χB = 0.121 ± 0.017 (stat) ± 0.006 (sys). Using the value of χd measured at the γ(4S) we derive the following limit for χs:χs > 0.16 (90% CL). © 1992

Determination of the number of light neutrino species

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 Nv = 3.14 ± 0.24 (stat.)±0.12 (syst.). This corresponds to an invisible Z$^0$ width of Γinv = 524 ± 40 ± 20 MeV

Measurement of inclusive production of neutral hadrons from Z decays

We present a study of the inclusive production of π0, η, Ks0 and Λ based on 929,000 hadronic Z decays recorded with the L3 detector at LEP. The measured inclusive momentum distributions have been compared with predictions from parton shower models as well as an analytical Quantum Chromodynamics calculation. Comparing to low energy e+e- data, we find that QCD describes the energy evolution of the hadron spectrum. © 1994

A measurement of τ\tau polarization at LEP

With a data sample of 86 000 Z → τ+τ-(γ) events collected in 1990 through 1993 we have measured the polarization of τ-leptons as a function of the production polar angle using the following 1-prong τ decay modes: τ-→e-vevτ, τ-→π- (K-)vτ, τ-→ρ{variant}-vτ and τ-→a1-vτ. We obtain for the ratio vector to axial-vector weak neutral couplings for electrons gVe/gAe=0.0791±0.0099(stat)±0.0025 (syst) and taus gVτ/gAτ=0.0752±0.0063 (stat)±0.0045 (syst) consistent with the hypothesis of e - τ universality. Assuming universality of the e - τ neutral current we determine the effective electroweak mixing angle to be sin2 θeffw = 0.2309 ± 0.0016. © 1994