On the Motion of Heavy Quarks Inside Hadrons: Universal Distributions and Inclusive Decays

In previous papers we have pointed out that there exists a QCD analog of the phenomenological concept of the so-called Fermi motion for the heavy quark inside a hadron. Here we show in a more detailed way how this comes about and we analyze the limitations of this concept. Nonperturbative as well as perturbative aspects are included. We emphasize both similarities and differences to the well-known treatment of deep inelastic lepton-nucleon scattering. We derive a model-independent lower bound on the kinetic energy of the heavy quark inside the hadron.