Tau physics: theoretical perspective

The leptonic decays of the τ lepton provide relevant tests on the structure of the weak currents and the universality of their couplings to the gauge bosons. The hadronic τ decay modes constitute an ideal tool for studying low-energy effects of the strong interaction in very clean conditions. Accurate determinations of the QCD coupling and the strange quark mass have been obtained with τ decay data. New physics phenomena, such as a non-zero mντ or violations of conservation laws can also be searched for with τ decays