Measurement of theB0-meson lifetime

We report a measurement of the lifetime of the ${\mathit{B}}^0$ meson based upon 29-GeV ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ annihilation data taken with the Mark II detector at the SLAC storage ring PEP. The ${\mathit{B}}^0$ mesons are tagged by their decays into ${\mathit{D}}^{\mathrm{*}\mathrm{-}}$ ${\mathit{e}}^{+}$ν and ${\mathit{D}}^{\mathrm{*}\mathrm{-}}$ ${\mathrm{\mu }}^{+}$ν, where the ${\mathit{D}}^{\mathrm{*}\mathrm{-}}$ is tagged by its decay into ${\mathrm{\pi }}^{\mathrm{-}}$D¯ ${}_{}{}^0{}_{}{}^{}$. We reconstruct the decay vertices of 15 ${\mathit{B}}^0$-meson candidates and measure the ${\mathit{B}}^0$ lifetime to be 1.${20}_{\mathrm{-}\mathrm{0.360.14}}^{+0.52+0.16\mathrm{}}$ psec.