Search for time-dependent $B_s^0-\overline{B_s^0}$ oscillations using a vertex charge dipole technique

We report a search for $B_s^0-\overline{B_s^0}$ oscillations using a sample of $400000$ hadronic $Z^0$ decays collected by the SLD experiment. The analysis takes advantage of the electron beam polarization as well as information from the hemisphere opposite that of the reconstructed B decay to tag the B production flavor. The excellent resolution provided by the pixel CCD vertex detector is exploited to cleanly reconstruct both B and cascade D decay vertices, and tag the B decay flavor from the charge difference between them. We exclude the following values of the $B_s^0-\overline{B_s^0}$ oscillation frequency: $\Delta m_s<4.9\mathrm{}{\mathrm{ps}}^{-1}$ and $7.9<\mathrm{}\Delta m_s<10.3\mathrm{}{\mathrm{ps}}^{-1}$ at the $95\%$ confidence level.