Measurement of the ${\mathit{B}}^{-}$ and ${\overline{B}}^0$ Meson Lifetimes Using Semileptonic Decays

The lifetimes of the $B^{-}$ and ${\overline{B}}^0$ mesons are measured using the partially reconstructed semileptonic decays $\overline{B}\to D{\ell }^{-}\overline{\nu }X$, where D is either a $D^0$ or $D^{*+}$ meson. The data were collected by the CDF detector at the Fermilab Tevatron collider during 1992–1993 and correspond to 19.3 ${\mathrm{pb}}^{-1\mathrm{}}$ of $\overline{p}p$ collisions at $\sqrt{s}=1.8\mathrm{}$ TeV. We measure the decay length distributions and find the lifetimes to be $\tau \left(B^{-}\right)=1.56\mathrm{}\pm 0.13\pm 0.06$ ps and $\tau \left({\overline{B}}^0\right)=1.54\mathrm{}\pm 0.08\pm 0.06$ ps, and the ratio of lifetimes to be $\tau \left(B^{-}\right)/\tau \left({\overline{B}}^0\right)=1.01\mathrm{}\pm 0.11\pm 0.02$, where the first uncertainties are statistical and the second are systematic.