Observation of the decay ${\mathit{B}}_{\mathit{s}}^0$→J/ψ φ in p¯p collisions at √s =1.8 TeV

This Letter reports the observation and mass measurement of fully reconstructed ${\mathit{B}}_{\mathit{s}}^0$ mesons through the decay chain ${\mathit{B}}_{\mathit{s}}^0$→J/ψ ψ, J/ψ→${\mathrm{\mu }}^{+}$${\mathrm{\mu }}^{\mathrm{-}}$, φ→${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{-}}$ using data obtained at the Collider Detector at Fermilab in p¯p collisions at √s =1.8 TeV. A signal of 14.0±4.7 events is observed. Comparison of the ${\mathit{B}}_{\mathit{s}}^0$ signal with the kinematically similar decays ${\mathit{B}}^{+}$→J/ψ ${\mathit{K}}^{+}$ and ${\mathit{B}}^0$→J/ψ ${\mathrm{K}}^{\mathrm{*}}$(892${)}^0$ is presented. The mass of the ${\mathit{B}}_{\mathit{s}}^0$ meson is determined to be 5383.3±4.5(stat)±5.0(syst) MeV/${\mathit{c}}^2$.