Measurement of theBs0Lifetime in the Exclusive Decay ChannelBs0→J/ψϕ

Using the exclusive decay ${B}_{s}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}({\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})\ensuremath{\phi}({K}^{+}{K}^{\ensuremath{-}})$, we report the most precise single measurement of the ${B}_{s}^{0}$ lifetime. The data sample corresponds to an integrated luminosity of approximately $220\text{ }\text{ }{\mathrm{p}\mathrm{b}}^{\ensuremath{-}1}$ collected with the D0 detector at the Fermilab Tevatron Collider in 2002--2004. We reconstruct 337 signal candidates, from which we extract the ${B}_{s}^{0}$ lifetime, $\ensuremath{\tau}({B}_{s}^{0})={1.444}_{\ensuremath{-}0.090}^{+0.098}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.020(\mathrm{s}\mathrm{y}\mathrm{s})\text{ }\text{ }\mathrm{p}\mathrm{s}$. We also report a measurement for the lifetime of the ${B}^{0}$ meson using the exclusive decay ${B}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}({\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}){K}^{*0}(892)({K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$. We reconstruct 1370 signal candidates, obtaining $\ensuremath{\tau}({B}^{0})={1.473}_{\ensuremath{-}0.050}^{+0.052}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.023(\mathrm{s}\mathrm{y}\mathrm{s})\text{ }\text{ }\mathrm{p}\mathrm{s}$, and the ratio of lifetimes, $\ensuremath{\tau}({B}_{s}^{0})/\ensuremath{\tau}({B}^{0})={0.980}_{\ensuremath{-}0.071}^{+0.076}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.003(\mathrm{s}\mathrm{y}\mathrm{s})$.