  Hadronic tau decays offer the possibility of determining the strong coupling
alpha_s at relatively low energy. Precisely for this reason, however, good
control over the perturbative QCD corrections, the non-perturbative condensate
contributions in the framework of the operator product expansion (OPE), as well
as the corrections going beyond the OPE, the duality violations (DVs), is
required. On the perturbative QCD side, the contour-improved versus fixed-order
resummation of the series is still an issue, and will be discussed. Regarding
the analysis, self-consistent fits to the data including all theory parameters
have to be performed, and this is also explained in some detail. The fit
quantities are moment integrals of the tau spectral function data in a certain
energy window and care should be taken to have acceptable perturbative
behaviour of those moments as well as control over higher-dimensional operator
corrections in the OPE.

High Energy Physics - Phenomenology