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

Using the exclusive decay $B_s^0\to J/\psi ({\mu }^{+}{\mu }^{-})\varphi (K^{+}{K}^{-})$, we report the most precise single measurement of the $B_s^0$ lifetime. The data sample corresponds to an integrated luminosity of approximately $220{\mathrm{p}\mathrm{b}}^{-1}$ 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, $\tau (B_s^0)={1.444}_{-0.090}^{+0.098}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.020(\mathrm{s}\mathrm{y}\mathrm{s})\mathrm{p}\mathrm{s}$. We also report a measurement for the lifetime of the $B^0$ meson using the exclusive decay $B^0\to J/\psi ({\mu }^{+}{\mu }^{-})K^{*0}(892)(K^{+}{\pi }^{-})$. We reconstruct 1370 signal candidates, obtaining $\tau (B^0)={1.473}_{-0.050}^{+0.052}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.023(\mathrm{s}\mathrm{y}\mathrm{s})\mathrm{p}\mathrm{s}$, and the ratio of lifetimes, $\tau (B_s^0)/\tau (B^0)={0.980}_{-0.071}^{+0.076}(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.003(\mathrm{s}\mathrm{y}\mathrm{s})$.