Measurement of the branching fractions of theτlepton using a tagged sample ofτdecays

The branching fractions for the major decay modes of the τ lepton are measured from a sample of tagged τ decays selected from ${\tau }^{+}$ ${\tau }^{\mathrm{-}}$ pairs produced in $e^{+}$ $e^{\mathrm{-}}$ annihilation. The decay products of one member of the ${\tau }^{+}$ ${\tau }^{\mathrm{-}}$ pair are used to identify the event. The opposite member of the pair is then included in the sample if it satisfies an invariant-mass cut and a charged-multiplicity cut. In this way, we attempt to select an unbiased sample of τ decays. The sample is divided into categories based on charged- and neutral-particle multiplicities, and charged-particle identification. The branching fractions are measured simultaneously, with an unfold technique and a maximum-likelihood fit, with the sum of the branching fractions constrained to be unity.