Direct Measurement of A[sub b] in Z[sup 0] Decays Using Charged Kaon Tagging

We present a direct measurement of the parity-violating asymmetry A[sub b] in the Z[sup 0] to b[ovr b] coupling using a new technique to distinguish the b and [ovr b] quarks using charged kaons from B decays. The Z[sup 0] bosons are produced in e[sup +]e[sup [minus]] collisions at the SLC with longitudinally polarized electrons. b[ovr b] events are selected using a secondary vertex mass tag and A[sub b] is determined from the left-right forward-backward asymmetry. From the 1994[endash]1995 data sample, selected from 100thinsp000 hadronic Z[sup 0] decays, we obtain A[sub b]=0.855[plus minus]0.088[sub stat][plus minus] 0.102[sub syst] . [copyright] [ital 1999] [ital The American Physical Society]