Search for B0s oscillations at D0

Measurement of the Bs0 oscillation frequency via Bs0 mixing analyses provides a powerful constraint on the CKM matrix elements. A search for Bs0 oscillations was performed using data collected by the D0 detector during the period 2002-2005 at the Fermilab Tevatron. Approximately 610 pb-1 of data was analyzed to reconstruct a large set of Bs0 mesons in different semileptonic decay modes. Opposite-side flavor tagging algorithms that were tested on semileptonic Bd0 decays with the measurement of the Bd0 mixing frequency were used to determine the initial state flavor of the reconstructed Bs0 meson. No significant signal for any particular value of the oscillation frequency was found. A 95% confidence level limit on the Bs0 oscillation frequency Δms > 7.3 ps-1 and a sensitivity of 9.5 ps-1 were obtained