Tau hadronic branching ratios

From 64492 selected tau-pair events, produced at the Zeta(o) resonance, the measurement of the tau decays into hadronsfrom a global analysisusing 1991, 1992 and 1993 ALEPHdata is presented. Special emphasis is given to the reconstruction of photons and pi(o)'s, and the removal of fake photons. A detailed study of the systematics entering the pi(o) reconstruction is also given. A complete and consistent set of tau hadronicbranching ratios is presented for 18 exclusive modes. Most measurements are more precise than the present world average. The new level of precision reached allows a stringent test of tau - mu universality in hadronicdecays, g(tau)/g(mu) = 1.0013 +/- 0.0095, and the first measurement of the vector and axial-vector contributions to the non-strange hadronictau decay width: R(tau,V) = 1.788 +/- 0.025 and R(tau,A) = 1.694 +/- 0.027. The ratio (R(tau,V) - R(tau,A))/(R(tau,V) + R(tau,A)), equal to (2.7 +/- 1.3) %, is a measure of the importance of QCD non-perturbative contributions to the hadronictau decay width.