S Mixing Using Inclusive and Semileptonic B Decays at Sld

We set a preliminary 95% C.L. exclusion on the oscillation frequency of B 0 s B 0 s mixing using a sample of 250,000 hadronic Z 0 decays collected by the SLD experiment at the SLC between January 1996 and March 1998. The analyses determine the b-hadron avor at production by exploiting the large forward-backward asymmetry of polarized Z 0 ! bb decays as well as information from the hemisphere opposite that of the reconstructed B decay. In one analysis, B decay v ertices are reconstructed inclusively with a topological technique, and separation between B 0 s and B 0 s decays exploits the B 0 s ! D s cascade charge structure. The other analysis selects semileptonic decays reconstructed by intersecting a lepton with the trajectory of a topologically reconstructed D meson. The two analyses are combined to exclude the following values of the B 0 s B 0 s mixing oscillation frequency: m s < 1:7 p s 1 and 3:3 < m s < 5:0 ps 1 at the 95% condence level.