ACAD SINICA,INST HIGH ENERGY PHYS,BEIJING,PEOPLES R CHINA
In the heavy quark limit, the heavy baryon Lambda(Q) (Q = b or c) can be regarded as composed of a heavy quark and a scalar light diquark which has good spin and flavor quantum numbers. Based on this picture we establish the Bethe-Salpeter (BS) equation for Lambda(Q) in the leading order of 1/m(Q) expansion. With the kernel containing both the scalar confinement and one-gluon-exchange terms we solve the BS equation numerically. The Isgur-Wise function for Lambda(b) --> Lambda(c) is obtained numerically from our model. A comparison with other model calculations is also presented. It seems that the Isgur-Wise function for Lambda(b) --> Lambda(c) drops faster than that for B --> D. The differential and total decay widths for Lambda(c)l(nu)over bar> are given in the limit m(b,c) --> infinity.