Heavy flavour physics at LEP

Since LEP started in 1989 each of the LEP experiment has recorded about 400000 hadronic Z0 decays; among them about 22% are expected to be b vector b quark decays. B event studies are expected to contribute to the electroweak sector measurements throught the forward backward asymetry measurement of the b quark decay and by the partial width measurement of Z0 → b vector b ; for this last point the measurement is actually limited by the uncertainties in the knowledge of the quark hadronisation mechanism and of the B meson electroweak decays. Improved measurements of the mixing parameter χ of B0 vector B0 oscillations and of the B lifetime contribute to the CKM matrix elements determination. Already with the 90 data the b lifetime has been measured by each of the 4 Lep experiment with an accuracy equivalent to the world average value, this measurement had been improved using 1991 statistics; in addition the use of lepton and charmed meson correlations has allowed the observation of ΛB and B0s throught exclusive decay channels, these signatures are already used for exclusive lifetime measurement of B0d, B0s, B+, ΛB. (orig.)