QCD predictions for lepton spectra in inclusive heavy flavor decays

We derive the lepton spectrum in semileptonic b decays from a nonperturbative treatment of QCD; it is based on an expansion in 1/${\mathit{m}}_{\mathit{Q}}$ with ${\mathit{m}}_{\mathit{Q}}$ being the heavy flavor quark mass. The leading corrections arising on the 1/${\mathit{m}}_{\mathit{Q}}$ level are completely expressed in terms of the difference in the mass of the heavy hadron and the quark. Nontrivial effects appear in 1/${\mathit{m}}_{\mathit{Q}}^2$ terms affecting mainly the end-point region; they are different for meson and baryon decays as well as for bottom and charm decays.