A Measurement of Pi-Polarization at Lep

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Measurement of the branching ratios b -> e nu Chi, mu nu Chi, tau nu Chi, and nu Chi

The inclusive semileptonic branching ratios b --> e nu X, mu nu X, tau nu X and nu X have been measured at LEP with the L3 detector. The analysis is based on 2-jet hadronic Z decays obtained in the data collected between 1991 and 1992. Three separate event samples are analysed, containing electrons, muons and large missing energy (neutrinos), respectively. From the electron sample, we measure Br(b --> e nu X) = (10.89+/-0.20+/-0.51)% and, from the muon sample, Br(b --> mu nu X) = (10.82+/-0.15+/-0.59)%, where the first error is statistical and the second is systematic. From the missing energy sample, we measure Br(b --> nu X) = (23.08+/-0.77+/-1.24)%, assuming the relative semileptonic decay rates e:mu:tau = 1:1:(0.25+/-0.05), according to theoretical expectations. From a combined analysis of all three samples and constraining the relative semileptonic rates, we measure Br(b --> e nu X) = Br(b --> mu nu X) = (10.68+/-0.11+/-0.46)%. Alternatively, we can remove the constraint on the relative semileptonic rates and measure Br(b --> tau nu X) = (1.7+/-0.5+/-1.1)%

Search for new particles in hadronic events with isolated photons

A search for the neutral Higgs boson in the processes e(+)e(-) --> Z --> H-0 gamma --> and e(+)e(-) --> Z --> Z*H-0 --> has been performed using 2.8 million hadronic Z decays collected with the L3 detector at LEP from 1991 through 1994. No evidence for these processes has been observed. Upper limits at 95% confidence level for the corresponding cross sections have been set and the results have been compared with theoretical predictions beyond the Standard Model