A Constraint On Vtd/Vts from B

We have searched for the decays, B ! aefl and B ! !fl, which in conjunction with the measurement of B ! K fl, can provide a direct determination of the ratio between the CKM matrix elements, V td and V ts . No signals were observed and we set the following upper limits (90% CL): B(B \Gamma ! ae \Gamma fl) ! 2:0 \Theta 10 \Gamma5 , B( ¯ B 0 ! ae 0 fl) ! 2:4 \Theta 10 \Gamma5 , and B( ¯ B 0 ! !fl) ! 1:1 \Theta 10 \Gamma5 . Using different theoretical models, we also set a range of upper limits on jV td =V ts j ! 0:64 -- 0.76. Permanent address: University of Hawaii at Manoa y Permanent address: INP, Novosibirsk, Russia Last year CLEO reported the first observation of B ! K fl, a flavor-changing neutral current (FCNC) penguin diagram decay [1]. This paper describes a search for three related FCNC penguin decays, B \Gamma ! ae \Gamma fl, ¯ B 0 ! !fl, and ¯ B 0 ! ae 0 fl mediated by the quark level process b ! dfl. The Feynman diagrams associat..