Measurement of theB−andB¯0Meson Lifetimes Using Semileptonic Decays

The lifetimes of the ${B}^{\ensuremath{-}}$ and ${\overline{B}}^{0}$ mesons are measured using the partially reconstructed semileptonic decays $\overline{B}\ensuremath{\rightarrow}D{\ensuremath{\ell}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}X$, 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 ${\mathrm{pb}}^{\ensuremath{-}1}$ of $\overline{p}p$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8$ TeV. We measure the decay length distributions and find the lifetimes to be $\ensuremath{\tau}({B}^{\ensuremath{-}})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.56\ifmmode\pm\else\textpm\fi{}0.13\ifmmode\pm\else\textpm\fi{}0.06$ ps and $\ensuremath{\tau}({\overline{B}}^{0})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.54\ifmmode\pm\else\textpm\fi{}0.08\ifmmode\pm\else\textpm\fi{}0.06$ ps, and the ratio of lifetimes to be $\ensuremath{\tau}({B}^{\ensuremath{-}})/\ensuremath{\tau}({\overline{B}}^{0})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.01\ifmmode\pm\else\textpm\fi{}0.11\ifmmode\pm\else\textpm\fi{}0.02$, where the first uncertainties are statistical and the second are systematic.