Measurement of the mass of the Bs0 meson in bar pp collisions at √s = 1.8 TeV

We measure the mass of the Bs0 meson by fully reconstructing the decay Bs0 → J/ψ φ with the subsequent decays J/ψ → μ+ μ- and φ → K+ K-. The data was obtained from 19.3 pb-1 of integrated luminosity of bar pp collisions at √s = 1.8 TeV using the Collider Detector at Fermilab (CDF). A sample of 80,000 inclusive J/ψ → μ+μ- events is used to study systematic biases in track reconstruction and is used to calibrate the momentum scale. We reconstruct the kinematically similar decays B- → J/ψ K- and B0 → J/ψ K* to study the mass measurement technique used for the B0 meson. Based on the observation of 32 ± 6 candidates, the mass of the Bs0 meson is measured to be 5369.9 ± 2.3 ± 1.3 MeV/c2