137-01137-01137-01-deformed extended Galilei algebra

We apply the pseudoextension mechanism, which in the undeformed case gives the centrally extended Galilei group {ie137-02} as a contraction of a trivial extensionP×U(1) of the Poincaré group, to the case of the-Poincaré algebra. As a result, the four-dimensional {ie137-03}-deformed extended Galilei algebra is obtained.Presented at the 4th Colloquium Quantum Groups and Integrable Systems, Prague, 22–24 June 1995.     

Determination of sin2 θ weff using jet charge measurements in hadronic Z decays

The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and backward hemisphere charges in hadronic decays of the Z. A data sample of 2.5 million hadronic Z decays recorded over the period 1990 to 1994 in the ALEPH detector at LEP is used. The mean charge separation between event hemispheres containing the original quark and antiquark is measured for and events in subsamples selected by their long lifetimes or using fastD*’s. The corresponding average charge separation for light quarks is measured in an inclusive sample from the anticorrelation between charges of opposite hemispheres and agrees with predictions of hadronisation models with a precision of 2%. It is shown that differences between light quark charge separations and the measured average can be determined using hadronisation models, with systematic uncertainties constrained by measurements of inclusive production of kaons, protons andΛ’s. The separations are used to measure the electroweak mixing angle precisely as sin² ϑ _w ^eff =0.2322±0.0008(exp.stat.) ±0.0007(exp.syst.)±0.0008(sep.). The first two errors are due to purely experimental sources whereas the third stems from uncertainties in the quark charge separations. Supported by Dirección General de Investigación Científica y Técnica, Spain     

Improved measurement of theB0 andB+ meson lifetimes

The lifetimes of theB ⁰ andB ⁺ mesons have been measured with theAleph detector at LEP, using approximately 3 million hadronic Z decays collected in the period 1991–1994. In the first of three methods, semileptonic decays ofB ⁰ andB ⁺ mesons were partially reconstructed by identifying events containing a lepton with an associatedD*⁻ or meson. The second method used fully reconstructedB ⁰ andB ⁺ mesons. The third method, used to measure theB ⁰ lifetime, employed a partial reconstruction technique to identifyB ⁰→D*⁻ π ⁺ X decays.