A measurement of the b [formula omitted] forward-backward asymmetry using the semileptonic decay into muons

Abstract

The forward-backward asymmetry of bottom quarks is measured with statistics of approximately 80 000 hadronic Z 0 decays produced in e +e − collisions at a centre of mass energy of √ s≈ M z. The tagging of b quark events has been performed using the semileptonic decay channel b→X+ μ. Because the asymmetry depends on the weak coupling, this leads to a precise measurement of the electroweak mixing angle sin 2θ w. The experimental result is A FB b = 0.115±0.043(stat.)±0.013(syst.). After correcting the value for the B 0 B 0 mixing this becomes A FB b =0.161±0.060(stat.)±0.021(syst.) corresponding to sin 2θ W MS =0.221±0.011( stat.)±0.004( syst.) .