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 $\overline{B}$ decay, and comment on the importance of nonresonant decays as testing grounds for very basic ideas on the structure, strength, and significance of the $q\overline{q}$ sea and on quark-hadron duality in QCD.