Measurement of the time-integrated neutral B meson mixing parameter in proton-antiproton collisions at 1.8 TeV

We measure, the time-integrated mixing parameter chi, in the neutral B meson system from pp¯ collisions at s = 1.8 TeV. B0 - B¯ 0 events are identified by semi-leptonic decays that result in e - mu pairs.{09}The measurement takes advantage of the charge correlation between the b quarks and the leptons from their semi-leptonic decays to relate chi to the ratio of like-sign to opposite-sign lepton pairs. The data set, of integrated luminosity 20 pb-1, was recorded during Run 1a at the Tevatron, by, the Collider Detector at Fermilab. We measure chi = 0.112 +/- 0.008 (stat.) +/- 0.013 (syst.).