Measurement of the mass of the Bs0 meson

We measure the mass of the ${\mathit{B}}_{\mathit{s}}^{0}$ meson by reconstructing the decay chain ${\mathit{B}}_{\mathit{s}}^{0}$\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\varphi}, J/\ensuremath{\psi}\ensuremath{\rightarrow}${\mathrm{\ensuremath{\mu}}}^{+}$${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$, and \ensuremath{\varphi}\ensuremath{\rightarrow}${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{\ensuremath{-}}}$. The data are obtained from 19.3 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$ of integrated luminosity of p\ifmmode\bar\else\textasciimacron\fi{}p collisions at \ensuremath{\surd}s=1.8 TeV using the Collider Detector at Fermilab. A sample of 80 000 inclusive J/\ensuremath{\psi}\ensuremath{\rightarrow}${\mathrm{\ensuremath{\mu}}}^{+}$${\mathrm{\ensuremath{\mu}}}^{\mathrm{\ensuremath{-}}}$ events is used to study systematic biases in track reconstruction and to calibrate the momentum scale. We reconstruct the kinematically similar decays ${\mathit{B}}^{+}$\ensuremath{\rightarrow}J/\ensuremath{\psi}${\mathit{K}}^{+}$ and ${\mathit{B}}^{0}$\ensuremath{\rightarrow}J/\ensuremath{\psi}${\mathit{K}}^{\mathrm{*}0}$ to study the mass measurement technique used for the ${\mathit{B}}_{\mathit{s}}^{0}$ meson. Based on the observation of 32 \ifmmode\pm\else\textpm\fi{} 6 candidates, the mass of the ${\mathit{B}}_{\mathit{s}}^{0}$ meson is measured to be 5369.9 \ifmmode\pm\else\textpm\fi{} 2.3 \ifmmode\pm\else\textpm\fi{} 1.3 MeV/${\mathit{c}}^{2}$ and the mass difference between ${\mathit{B}}_{\mathit{s}}^{0}$ and the average mass of ${\mathit{B}}^{+}$ and ${\mathit{B}}^{0}$ is determined to be 89.7 \ifmmode\pm\else\textpm\fi{} 2.7 \ifmmode\pm\else\textpm\fi{} 1.2 MeV/${\mathit{c}}^{2}$. \textcopyright{} 1996 The American Physical Society.