Analytical methods in heavy quark physics and the case of $\tau_{1/2}(w)$

Abstract

Analytical methods in heavy quark physics are shortly reviewed, with emphasis on the problems of dynamical calculations. Then, attention is attracted to the various difficulties raised by a tentative experimental determination of $\tau_{1/2}$Comment: 10 pages, FPCP2003 conference (Paris) [typos corrected,new references