Time Dependent B 0 ¯ B 0 Mixing at CDF

Measurements of the frequencies for Bd and Bs mesons to oscillate into B̄d and B̄s, respectively, can potentially constrain the magnitudes of the CKM matrix elements Vts and Vtd. These frequencies are proportional to ∆md and ∆ms, the mass differences between the CP eigenstates of the Bd and Bs mesons. Recent measurements have provided precise determinations of ∆md and lower limits on ∆ms . The large bb̄ cross-section in pp̄ collisions at √ s = 1.8 GeV has enabled the reconstruction of large B signals using the CDF detector . The measurement of a time-dependent mixing probability is made possible by a precise decay length measurement from the Silicon Vertex Detector (SVX) . The charges of the decay products tag the flavor of the B at the time of decay. To tag the flavor of the B at production, several tagging algorithms have been developed. The measurement of the mistag probabilities of these algorithms is also useful for future measurements of CP violation . We present herein two measurements of the Bd mixing frequency. The first uses semileptonic B decays in which the charm has been fully reconstructed, and a same-side flavor tagging algorithm using correlations between B mesons and charged tracks. Such correlations have been observed at LEP 5 and in B → J/ψK events at CDF . The second uses semileptonic B decays in which the charm has been inclusively reconstructed, and a flavor tagging algorithm using the semileptonic decay of the other B in the event.