Measurement of theB−andB0meson lifetimes using semileptonic decays

The lifetimes of the $B^{-}$ and $B^0$ mesons are measured using the partially reconstructed semileptonic decays $\overline{B}\to {\mathrm{Dl}}^{-}\overline{\nu }X,$ where $D$ is either a $D^0$ or $D^{*+}$ meson. The data were collected by the CDF detector at the Fermilab Tevatron collider during 1992–1995 and correspond to about $110{\mathrm{pb}}^{\mathrm{-}1}$ of $\overline{p}p$ collisions at $\sqrt{s}=1.8\mathrm{}\mathrm{TeV}.$ We measure decay lengths and extract the lifetimes to be $\tau {(B}^{-})=1.637\mathrm{}\pm {0.058}_{-0.043}^{+0.045\mathrm{}}$ ps and $\tau \left(B^0\right)=1.474\mathrm{}\pm {0.039}_{-0.051}^{+0.052\mathrm{}}\mathrm{ps},$ and the ratio of the lifetimes to be $\tau {(B}^{-})/\tau (B^0)=1.110\mathrm{}\pm {0.056}_{-0.030}^{+0.033\mathrm{}},$ where the first uncertainties are statistical and the second are systematic.