The inclusive semileptonic branching ratios b —► e u X , uX , r vX and vX have been measured at LEP with a Supported by the German Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie b Supported by the Hungarian OTKA fund under contract number T 14459 c Supported also by the Comisión Interministerial de Ciencia y Technologia d Also supported by CONICET and Universidad Nacional de La Plata, CC 67, 1900 La Plata, Argentina e Also supported by Panjab University, Chandigarh-160014, India 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, contain­ ing electrons, muons and large missing energy (neutrinos), respectively. From the electron sample, we measure Br(b —> ez/X) (10.89±0.20=b0.51)% and, from the muon sam­ ple, Br(b —► ¡jl vX ) = (10.82±0.15±0.59)%, where the first error is statistical and the second is systematic. From

Using a sample of e + e " annihilation events collected with the L3 detector at the Z resonance corresponding to an integrated luminosity of 137 p b _ we have searched for anomalous production o f y X final states where X represents stable, weakly interacting particles and the photon energy is greater than 15 GeV. The sample of events found is consistent with Standard Model expectations. Upper limits are set on Z y couplings, the r neutrino magnetic moment, and the branching ratio for Z -> y X . © 1997 Elsevier Science B.V. 6 Supported also by the Comisión Interministerial de Ciencia y Technología, M. Acciarri et a l . / Physics Letters B 412 (1997) 201-209 205

We present evidence for soft gluon interference, as required by QCD. This interference is expected to manifest itself in an angular ordering of the gluons radiated within a jet. Using hadronic decays of the Z boson in the L3 detector at LEP, we compare variables sensitive to such an angular ordering, namely the energy-energy correlation asymmetry and the newly introduced particle-particle correlation asymmetry, with the predictions of various parton shower models. Only those models which incorporate the expected interference agree with the data.

Time-dependent Bz-@ mixing is studied using 1.5 million hadronic Z decays collected by L3. Semileptonic B decays are selected by requiring at least one reconstructed lepton in both thrust hemispheres. Charge correlations between the tagged leptons are studied as a function of proper time. The proper time of the b-hadron decay is measured by reconstructing the production and decay vertices using a silicon microvertex detector. The measured Bz meson oscillation frequency corresponds to a mass difference Am& between the two B’: mass eigenstates of Amd = (0.496+‘:;!:;, (stat) k 0.043 (syst)) ps-‘.

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The e+e− → e+e−K0SK±π∓ and e+e− → e+e−ηπ+π− final states are studied with the L3 detector at LEP using data collected at centre-of-mass energies from 183 GeV up to 202 GeV. The mass spectrum of the K0 SK ±π∓ final state shows an enhancement around 1470 MeV, which is identified with the pseudoscalar meson η(1440). This state is observed in γ γ collisions for the first time and its two-photon width is measured to be Γγγ (η(1440)) × BR(η(1440) → K Kπ) = 212 ± 50 (stat.) ± 23 (sys.) eV. Clear evidence is also obtained for the formation of the axial vector mesons f1(1420) and f1(1285). In the ηπ+π− channel the f1(1285) is observed, and upper limits for the formation of η(1440) and η(1295) are obtained.  2001 Published by Elsevier Science B.V.

This report is an overview of the gamma-gamma physics capabilities of LEP2, and covers the following topics: structure functions, equivalent photon approximation, tagging conditions etc, soft and semihard physics, large-$p_t$ processes, heavy-quark physics, and exclusive channels.

We present a study of the structure of hadronic events recorded by the L3 detector at center-of-mass energies of 130 and 136 GeV. The data sample corresponds to an integrated luminosity of 5 pb-’ collected during the high energy run of 1995. The shapes of the event shape distributions and the energy dependence of their mean values are well reproduced by QCD models. From a comparison of the data with resummed (?(a:) QCD calculations, we determine the strong coupling constant to be LY~ ( 133 GeV ) = 0.107 f 0.005 (exp) f 0.006( theor).