$B_s$ Mixing at SLD

Abstract

We set a preliminary 95% C.L. exclusion on the oscillation frequency of $B_s^0 - \bar{B_s^0}$ mixing using a sample of 400,000 hadronic $Z^0$ decays collected by the SLD experiment at the SLC during the 1996-98 run. Three analyses are presented in this paper. The first analysis partially reconstructs the $B_s^0$ by combining a fully reconstructed $D_s$ with the remaining charged B decay tracks. The second analysis selects a sample of events with a partially reconstructed charm vertex and a lepton track. The third analysis reconstructs b-hadrons topologically and exploits the $b \to c$ cascade charge structure to determine the flavor of the b-hadron at decay. All three analyses take advantage of the large forward-backward asymmetry of the polarized $Z^0 \to b \bar{b}$ decays and information in the hemisphere opposite to the reconstructed B vertex to determine the b-hadron flavor at production. The results of the three analyses are combined to exclude the following values of the $B_s^0 - \bar{B_s^0}$ oscillation frequency: $\Delta m_s < 7.6 ps^{-1}$ and $11.8 < \Delta m_s < 14.8 ps^{-1}$ at the 95% confidence level.