New results on electroweak b physics from LEP

Summary

Recent results from LEP on selected topics in electroweak physics involving-b quark events are reviewed. The LEP average value of the Z⁰ partial width to b-quarks is:$\Gamma _{b\bar b} = 0.220 \pm 0.003$ giving the limit on the top-quark mass:m _t<230 GeV/c² (95% c.l.). The b-quark forward-backward asymmetry leads to a measurement of the effective Weinberg angle, sin² θ_eff=0.2299±0.0017 and the semi-leptonic b-quark decay branching ratio is measured to be, BR (b→ℓ)=0.110±0.005. Results on time-averaged and time-dependent$B^0 - \bar B^0$ mixing are presented, the latter leading to a measurement of the mass difference of the B⁰ and$\bar B^0$ mesons: Δm=[3.44 ^+0.65_−0.70 (stat) ^+0.22_−0.16 (syst)]·10⁻⁴ eV.