Univ Adelaide, Dept Phys & Math Phys, Adelaide, SA 5005, Australia
; Univ Adelaide, Sepcial Res Ctr Subatom Struct Matter, Adelaide, SA 5005, Australia
; Acad Sinica, Inst High Energy Phys, Beijing 100039, Peoples R China
; CCAST, World Lab, Beijing 100080, Peoples R China
; Nankai Univ, Dept Phys, Tianjin 300071, Peoples R China
In the heavy quark limit a heavy baryon which contains two heavy quarks is believed to be composed of a heavy diquark and a light quark. Based on this picture, we evaluate the weak semileptonic decay rates of such baryons. The transition form factors between two heavy baryons are associated with those between two heavy mesons by applying superflavor symmetry. The effective vertices of the W boson and two heavy diquarks are obtained in terms of the Bethe-Salpeter equation. Numerical predictions on these semileptonic decay widths are presented and they will be tested in future experiments. [S0556-2821(98)00721-8].