Measurement of the b forward-backward asymmetry and mixing using high-p(perpendicular to) leptons

The B-0-B-0 average mixing parameter and b forward-backward asymmetry A(FB)(0)(b) are measured from a sample of about 4200000 Z--> events recorded with the ALEPH detector at LEP in the years 1990-1995. High transverse momentum electrons and muons produced in b semileptonic decays provide the tag of the quark flavour and of its charge.The average mixing parameter and the pole b asymmetry are measured to be =0.1246+/-0.0051(stat)+/-0.0052(syst), A(FB)(0)(b)=0.1008+/-0.0043(stat)+/-0.0028(syst). The value of sin(2) theta(W)(eff)=0.23198+/-0.00092 is extracted from the asymmetry measurement.