Nonresonant semileptonic heavy quark decay

In both the large N-c limit and the valence quark model, semileptonic decays are dominated by resonant final states. Using Bjorken's sum rule in an "unquenched" version of the quark model, I demonstrate that in the heavy quark limit nonresonant final states should also be produced at a significant rate. By calculating the individual strengths of a large number of exclusive two-body nonresonant channels, I show that the total rate for such processes is highly fragmented. I also describe some very substantial duality-violating suppression factors which reduce the inclusive nonresonant rate to a few percent of the total semileptonic rate for the finite quark masses of (B) over bar decay, and comment on the importance of nonresonant decays as testing grounds for very basic ideas an the structure, strength, and significance of the q (q) over bar sea and on quark-hadron duality in QCD. [S0556-2821(99)03817-5].