A precise measurement of the $B^0_s$ lifetime

We report the lifetime measurement of the flavor--specific $B_s^0$ meson decay $B^0_{s}\rightarrow D^-_s \mu^{+}\nu X$, using approximately 400 pb$^ {-1}$ of data collected by the D\O\ detector during 2002--2004. We have reconstructed 5176 $D^-_s \mu^{+}$ candidate events, from which we have measured the $B^0_s$ lifetime with a combined statistical and systematic uncertainty of less than 16 $\mu$m which is the currently most precise measurement of the $B_s^0$ lifetime.