Measurement of the topological and hadronic decay branching fractions of the tau lepton with the L3 detector at LEP

Using the data collected with the L3 detector at LEP during 1992-1995 run at the 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 tracks are studied and rejected in the analysis. The decay channels are identified using a set of neural networks. The topological tau decay branching fractions are B( tau to 1-prong) =85.14+or-0.27+or-0.17%, B( 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%. 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 h/sup 2/ pi /sup 0/ nu )= (8.98+or-0.21+or-0.19)%, BR( tau to 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)%, where the first error is statistical and the second systematic. (13 refs).