B_S MIXING AT SLD

摘要

A preliminary 95% C.L. exclusion on the oscillation frequency of B_s~0 -(B_s~0)~- mixing is presented by combining three analyses of a sample of 400,000 hadronic Z~0 decays collected by the SLD experiment at the SLC between 1996 and 1998. All three analyses exploit 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, to determine the b-hadron flavor at production. The three analyses differ in their reconstruction of the proper time and flavor of the b-hadron at decay. The first analysis performs a full reconstruction of a cascade D_s meson and a partial reconstruction of the b-hadron. In the second analysis, semileptonic decays arc selected and the B decay point is reconstructed by vcrtcxing a lepton with a partially reconstructed cascade D meson. The third analysis reconstructs B decay vertices inclusively using a topological technique, with separation between B_s~0 and (B_s~0)~- decays obtained by exploiting the B_s~0 → D_s~- cascade charge structure. The results of these analyses are combined to exclude the following values of the B_s~0 -(B_s~0)~- mixing oscillation frequency: Δm_s < 7.6 ps~(-1) and 11.8 < Δm_s < 14.8 ps~(-1) at the 95% confidence level.