Measurement ofD s + meson production inZ decays and of theB s 0 lifetime

D s + mesons produced inZ 0→bb events were separated from theZ 0→cc component using a lifetime tag. Using a sample of 1.5 million hadronicZ decays collected with theAleph detector theB s 0 andD s + yields have been measured:\(\begin{gathered} \hfill B(b \to \bar B_s^0 )B(\bar B_s^0 \to D_s^ + ) = 0.088 \pm 0.020( stat.) \\ \hfill \pm 0.020( stat.) \\ \hfill B(c \to D_s^ + ) = 0.088 \pm 0.020( stat.)_{ - 0.016}^{ + 0.019} (syst.) \\ \end{gathered} \) TheB s 0 lifetime was measured in aB s 0 enriched sample reconstructing the decay length from the vertex of theD s + with a hadron from theB s 0 decay. The result obtained is:\(\tau _{B_s } = 1.61_{ - 0.29}^{ + 0.30} ( stat.)_{ - 0.016}^{ + 0.018} (syst.)\) ps.