Study on the property of $\tau$ hadronic decays

Using the data collected with the L3 detector at LEP during 1992-1995 run at Z/sup 0/ peak, corresponding to an integrated luminosity of 92.63 pb/sup -1/, the topological and hadronic tau decay branching fractions are measured. Photon conversion, fake photon and backlash are studied and rejected in the analysis. The decay channels are identified using a set of neural networks. By fitting neural network output spectra with the binned maximum likelihood method the branching fractions of tau hadronic decays are determined: BR( tau to h nu )=(12.51 +or- 0.12 +or- 0.13)%, BR( tau to h pi /sup 0/ nu )= (25.38 +or- 0.18 +or- 0.14)% BR( tau to h2 pi /sup 0/ nu )=(8.98 +or- 0.21 +or- 0.19)%, BR( tau to h >or= 3 pi /sup 0/ nu )=(1.77 +or- 0.14 +or- 0.15)% BR( tau to 3h nu )=(9.11 +or- 0.15 +or- 0.08)%, BR( tau to 3h pi /sup 0/ nu )=(4.77 +or- 0.19 +or- 0.10)% , BR( tau to 3h >or = 2 pi /sup 0/ nu )=(0.45 +or- 0.10 +or- 0.11)%. And the topological tau decay branching fractions are B( tau to 1-prong) = 85.14 +or- 0.27 +or- 0.17%, B( tau to 3-prong) = 14.63 +or- 0.13 +or- 0.10% and B( tau to 5-prong) = 0.23 +or- 0.01 +or- 0.05%, where the first error is statistical and the second systematic. (6 refs).