A precision measurement of the branching fraction B( τ± → h±π0ντ) from CLEO II

Using data from the CLEO II detector at CESR, we measure B( τ^± → h^±π⁰ν_τ) where h^± refers to either π^± or K^±. We use τ⁺τ^- events in which one tau decays to h^±π⁰ν _τ and the other decays into either e^±ν_eν _τ, μ^±ν_μν_τ, h^±π⁰ν_τ, or h^±h⁺h^-( π⁰) ν_τ. We use three different methods to measure this branching fraction. The combined result is B( τ^± → h^±π⁰ν_τ) = 0.2587 ± 0.0012 ± 0.0042, in good agreement with predictions from CVC. This result, in combination with other precision measurements, reduces the significance of the one-prong problem in tau decays. Preliminary results from a fit to the π^±π⁰ mass distribution are also presented.