Exclusive and inclusive semileptonic Lambda(b)-decays

In this talk we present theoretical evidence Chat the exclusive/inclusive r atio of semileptonic Lambda (b)-decays exceeds that of semileptonic B-decay s, where the experimental exclusive/inclusive ratio amounts to about 66%. W e start from the observation that the spectator quark model provides a lowe r bound on the leading order Isgur-Wise function of the Lambda (b) -> Lambd a (c) transition in terms of the corresponding B -> D, D-* mesonic Isgur-Wi se function. Using experimental data for the B -> D, D-* masonic Isgur-Wise functions this bound is established. Applying a QCD sum rule estimate of t he Lambda (b) -> Lambda (c) transition form factor which satisfy the specta tor quark model bound we predict the exclusive/inclusive ratio of semilepto nic Lambda (b) decay rates to lie in a range between 0.81 and 0.89. We also provide an upper bound on the baryonic Isgur-Wise function which is determ ined from the requirement that the exclusive rate should not exceed the inc lusive rate. Our pre-Osaka results are discussed in the light of new recent preliminary experimental results on the pertinent mesonic and baryonic for m factors presented at the Osaka ICHEP 2000 Conference.