Measurement of theB0B0oscillation frequency usingl−D*+pairs and lepton flavor tags

The oscillation frequency {delta}m{sub d} of B{sup 0}B(bar sign){sup 0} mixing is measured using the partially reconstructed semileptonic decay B(bar sign){sup 0}{yields}l{sup -}{nu}(bar sign)D{sup *+}X. The data sample was collected with the CDF detector at the Fermilab Tevatron collider during 1992-1995 by triggering on the existence of two lepton candidates in an event, and corresponds to about 110 pb{sup -1} of p(bar sign)p collisions at {radical}(s)=1.8 TeV. We estimate the proper decay time of the B(bar sign){sup 0} meson from the measured decay length and reconstructed momentum of the l{sup -}D{sup *+} system. The charge of the lepton in the final state identifies the flavor of the B(bar sign){sup 0} meson at its decay. The second lepton in the event is used to infer the flavor of the B(bar sign){sup 0} meson at production. We measure the oscillation frequency to be {delta}m{sub d}=0.516{+-}0.099{sub -0.035}{sup +} {sup 0.029} ps{sup -1}, where the first uncertainty is statistical and the second is systematic. (c) 1999 The American Physical Society.