Heavy Quarks: Effective Theories, Lattice and Models

Heavy-light mesons, heavy quarkonium and doubly heavy baryons are briefly discussed. Effective field theories (EFTs) of QCD based on the heavy quark mass expansion 1/m_Q provide a unified framework to describe all three systems. They produce a number of model-independent results and simplify non-perturbative (lattice) calculations. Nevertheless, models are still very useful to obtain inexpensive estimates of many observables. It is emphasized that certain models can be accommodated in the EFT framework, like non-relativistic potential models for heavy quarkonium. It is also outlined how to build a suitable EFT for doubly heavy baryons which might also accommodate existing models for these systems. Finally, a few lattice calculations which are badly needed as inputs for EFTs are pointed out.